Author: Mark Valderrama

Table of Contents

• What Care Guides Get Wrong
• Key Takeaways
• Species Overview
• Classification
• Origin & Natural Habitat
• Appearance & Identification
• Average Size & Lifespan
• Care Guide
• Is It Right for You?
• Tank Mates
• Food & Diet
• Breeding & Reproduction
• Common Health Issues
• Common Mistakes to Avoid
• Where to Buy
• Frequently Asked Questions
• Species Comparison
• Closing Thoughts
• Recommended Video
• References

The exclamation point rasbora is one of those nano fish that earns its name in the best possible way. Take a close look at Boraras urophthalmoides and you’ll see a bold dark lateral stripe that ends in a distinct round spot near the base of the tail — it looks exactly like an exclamation point (!). It’s one of the most clever common names in the hobby, and once you see it, you can’t unsee it.

What Most Care Guides Get Wrong About the Exclamation Point Rasbora

The Exclamation Point Rasbora is one of the tiniest fish in the hobby, and people consistently underestimate just how small it is. We are talking about an adult that barely reaches 0.8 inches. The misconception is that it will be visible and impactful in a standard community tank. It will not. In a 55-gallon tank with larger fish, you will never see them. These fish need a dedicated nano setup where they are the feature species, not an afterthought. The other mistake is filtration. standard HOB filters can literally suck them up.

What really sets this species apart from other Boraras is availability. The exclamation point rasbora is the most widely available species in the genus, and for good reason — it has a much broader natural range than its cousins, spanning Thailand, Vietnam, and Cambodia rather than being restricted to a single river system or island. That wider distribution means more collection points and more consistent supply in the trade. If you’ve been wanting to try a Boraras species but couldn’t find chili rasboras or dwarf rasboras at your local shop, there’s a good chance you’ll have better luck with this one.

In my 25+ years in the hobby, I’ve watched the nano fishkeeping movement grow from a niche curiosity into one of the most popular areas of the freshwater side. The exclamation point rasbora is a big part of that story — a tiny, peaceful, beautifully marked fish that thrives in planted nano tanks and looks incredible in groups. Let’s get into everything you need to know to keep them well.

Key Takeaways

• Tiny but striking — maxes out at just 0.8 inches (2 cm), with a distinctive dark stripe and spot pattern that resembles an exclamation point
• The most widely available Boraras species thanks to a broader natural range across Thailand, Vietnam, and Cambodia
• Thrives in soft, acidic water with a pH of 5.0 to 7.0 and hardness of 1 to 8 dGH — more flexible than some other Boraras species
• Peaceful nano schooling fish that should be kept in groups of at least 8 to 10 for best color and natural behavior
• Perfect for planted nano tanks as small as 5 gallons (19 liters) — dark substrate and tannin-stained water really make the colors pop
• Egg scatterer that can breed in well-maintained tanks, though raising the tiny fry takes patience and very small first foods

Species Overview

Field	Details
Scientific Name	Boraras urophthalmoides (Kottelat, 1991)
Common Names	Exclamation Point Rasbora, Least Rasbora, Sparrow Rasbora
Family	Danionidae
Origin	Southeast Asia (Thailand, Vietnam, Cambodia)
Care Level	Easy
Temperament	Peaceful
Diet	Omnivore (micropredator)
Tank Level	Middle
Maximum Size	0.8 inches (2 cm)
Minimum Tank Size	5 gallons (19 liters)
Temperature	73 to 82°F (23 to 28°C)
pH	5.0 to 7.0
Hardness	1 to 8 dGH
Lifespan	3 to 5 years
Breeding	Egg scatterer
Breeding Difficulty	Moderate
Compatibility	Nano community
OK for Planted Tanks?	Yes — ideal choice

Classification

Taxonomic Level	Classification
Order	Cypriniformes
Family	Danionidae (formerly placed in Cyprinidae)
Subfamily	Rasborinae
Genus	Boraras
Species	B. urophthalmoides (Kottelat, 1991)

The exclamation point rasbora was described by Maurice Kottelat in 1991 as Rasbora urophthalmoides. When Kottelat established the genus Boraras in 1993 to accommodate miniature rasbora-like cyprinids, this species was transferred into the new genus along with several other micro-sized relatives. The genus name Boraras is an anagram of Rasbora, a clever taxonomic nod to the close relationship between these tiny fish and their larger cousins.

The species name urophthalmoides comes from the Greek “uro” (tail), “ophthalmos” (eye), and “oides” (resembling) — a reference to the prominent eye-like spot near the tail. Currently, the genus Boraras contains six recognized species, all of which stay well under 1 inch (2.5 cm). Other popular species in the genus include the chili rasbora (B. brigittae), dwarf rasbora (B. maculatus), and phoenix rasbora (B. merah). Like all rasboras, this species was historically classified under Cyprinidae but has been reclassified into Danionidae based on molecular phylogenetic studies.

Origin & Natural Habitat

The exclamation point rasbora has one of the widest natural ranges in the Boraras genus. While most of its relatives are confined to the Malay Peninsula or individual Indonesian islands, B. urophthalmoides is found across mainland Southeast Asia — specifically in Thailand (including the Mekong basin), Vietnam, and Cambodia. This broader distribution is a big part of why this species is the most consistently available Boraras in the aquarium trade.

In the wild, these fish inhabit slow-moving or still waters associated with floodplains, rice paddies, peat swamps, and shallow forest streams. The water is typically shallow, warm, and soft with an acidic to neutral pH. Many of these habitats have a substrate of mud, decomposing leaf litter, and organic debris, which stains the water a characteristic tea-brown color from released tannins and humic acids. Vegetation — both submerged aquatic plants and overhanging terrestrial plants — provides shade and cover.

Water movement in these habitats is typically minimal or nonexistent, especially during the dry season when the fish may be confined to shallow pools and ditches. The exclamation point rasbora shares its habitat with other small cyprinids, gouramis, and various invertebrates. The rice paddy connection is particularly interesting — these fish have adapted to a seasonal environment where water levels fluctuate dramatically, and they can thrive in surprisingly shallow water as long as it stays warm and clean.

Understanding this natural environment is key to replicating it in the aquarium. Slow flow, warm temperatures, soft acidic water, dense planting, and leaf litter all mimic the conditions where these fish evolved and bring out their best colors and behavior.

Appearance & Identification

The exclamation point rasbora is a tiny, slender-bodied fish with a translucent to golden-tan base color that can range from pale amber to a warm reddish-orange depending on condition, water chemistry, and diet. In well-maintained soft water with tannins, the overall coloration becomes warmer and more vibrant.

The feature that gives this species its unforgettable common name is the dark lateral marking. A prominent dark stripe runs along the midline of the body, tapering as it moves toward the tail and terminating in a bold, round dark spot at the base of the caudal fin. Together, the stripe and spot create a shape that looks remarkably like an exclamation point — it’s one of the most distinctive field marks of any nano fish. There is also typically a smaller dark marking near the base of the anal fin.

The fins are mostly transparent, sometimes with a faint yellowish or reddish tinge. The body has a slight iridescent sheen under certain lighting conditions, and the eye is proportionally large with a dark pupil and a thin golden iris. While not as intensely red as the chili rasbora, the exclamation point rasbora has a subtle beauty that really comes into its own in a densely planted tank with dark substrate and subdued lighting.

Telling Boraras Species Apart

Mislabeling among Boraras species is common in the trade, so knowing what to look for matters. Here’s how to distinguish the exclamation point rasbora from its closest relatives:

• Exclamation point rasbora (B. urophthalmoides) — dark lateral stripe ending in a round caudal spot (the “exclamation point” pattern); body is golden-tan to amber
• Chili rasbora (B. brigittae) — intense red body with a dark lateral stripe but no distinct round caudal spot; the stripe is bordered by bright red pigment
• Dwarf rasbora (B. maculatus) — ruby-red body with three separate dark blotches (mid-body, anal fin base, caudal peduncle) rather than a continuous stripe
• Phoenix rasbora (B. merah) — reddish body with a dark lateral blotch (not a stripe) flanked by red or orange; often confused with B. brigittae
• Strawberry rasbora (B. naevus) — single large dark blotch on mid-body; generally less intensely colored than other Boraras
• Micro rasbora (B. micros) — very small with a dark blotch and reduced lateral stripe; the least commonly seen species in the trade

Male vs. Female

Sexing exclamation point rasboras takes a careful eye, but it’s doable once you know what to look for. Females tend to be slightly larger and rounder-bodied than males, especially when carrying eggs — a gravid female will have a noticeably plumper belly. Males are generally slimmer and may display slightly more intense coloration, particularly along the lateral stripe and around the fins. During spawning condition, males can develop a deeper amber or reddish tone. The differences are subtle, though, and you’ll usually need a group of adults in good condition to compare side by side.

Average Size & Lifespan

The exclamation point rasbora is a true micro fish. Adults max out at about 0.8 inches (2 cm) in total length, with most specimens in home aquariums reaching around 0.6 to 0.7 inches (1.5 to 1.8 cm). They’re one of the smallest fish you can keep in an aquarium, and first-time owners are often surprised by just how tiny they really are in person.

With proper care — stable water parameters, good diet, low stress — exclamation point rasboras can live 3 to 5 years in captivity. That’s a solid lifespan for such a small fish. The key to longevity is consistency. These fish don’t handle big swings in temperature or water chemistry well, and keeping their environment stable goes a long way toward a full, healthy lifespan.

Care Guide

Tank Size

A 5-gallon (19-liter) tank is the minimum for a small school of exclamation point rasboras. These are tiny fish that don’t need a lot of swimming room, but they do need to be kept in groups — and a 5-gallon gives you enough space for a school of 8 to 10 comfortably. If you want a larger group of 15 or more (which really shows off their natural schooling behavior), bump up to a 10-gallon (38-liter) tank.

Nano tanks in the 5 to 10-gallon range are honestly ideal for this species. In a big community tank, these micro fish tend to get lost and can feel threatened by larger tank mates. A dedicated nano setup lets you really appreciate their subtle beauty and natural behavior up close.

Water Parameters

Parameter	Ideal Range
Temperature	73 to 82°F (23 to 28°C)
pH	5.0 to 7.0
Hardness	1 to 8 dGH
KH	1 to 6 dKH

The exclamation point rasbora prefers soft, acidic water, though it’s a bit more tolerant than some of its Boraras relatives. That 1 to 8 dGH range gives you more flexibility than, say, the dwarf rasbora which really wants ultra-soft water. That said, these fish will look their absolute best and show their strongest coloration in the lower end of these ranges — soft water around 1 to 4 dGH with a pH of 5.5 to 6.5 is the sweet spot.

Captive-bred specimens (which make up most of the supply in the trade) tend to be more adaptable to moderate water conditions than wild-caught fish. Even so, avoid hard, alkaline water if you can. Stability is more important than hitting a perfect number — pick a target within the range and keep it consistent. Weekly water changes of 20 to 25% with matched temperature and chemistry will keep things stable.

Filtration & Water Flow

A gentle sponge filter is the go-to choice for exclamation point rasboras. These fish come from still or barely moving water in the wild, so strong current from a hang-on-back or canister filter is too much for them. A sponge filter powered by a small air pump provides the perfect combination of biological filtration and gentle water movement without blasting these tiny fish around the tank.

If you prefer a small HOB filter, baffle the outflow with a sponge or pre-filter to reduce current. The fish should be able to swim comfortably without constantly fighting against flow. Water changes of 20 to 25% weekly are recommended — use a slow siphon or airline tubing to avoid accidentally sucking up these tiny fish during maintenance.

Lighting

Subdued to moderate lighting works best. In the wild, exclamation point rasboras live in shaded habitats with heavy canopy cover, and they naturally feel more comfortable and display better color under dimmer conditions. If you’re running a planted tank that needs moderate light for plant growth, use floating plants like Amazon frogbit, salvinia, or red root floaters to create shaded areas where the fish can retreat.

Under bright, unshaded lighting, these fish tend to wash out and may stay hidden. Tannin-stained water from Indian almond leaves or driftwood also helps diffuse light naturally and creates a more comfortable environment that encourages bolder behavior.

Plants & Decorations

A heavily planted tank is the way to go with this species. Dense clusters of fine-leaved plants like Java moss, Christmas moss, Cryptocoryne species, and Rotala rotundifolia provide cover and make the fish feel secure. Floating plants are a must for the shading benefits mentioned above.

Driftwood and Indian almond leaves are excellent additions — they release tannins that soften the water, lower pH slightly, and stain the water a natural tea-brown color that mimics the fish’s wild habitat. Leaf litter (dried Indian almond leaves, oak leaves, or catappa bark) on the substrate adds a natural touch and also provides microorganism growth that the fish will pick at between feedings. Leave some open swimming space in the middle or front of the tank so you can actually watch the school move together.

Substrate

Dark substrate is strongly recommended. A fine, dark sand or aqua soil makes the exclamation point rasbora’s coloration pop dramatically compared to light-colored gravel. Beyond aesthetics, dark substrate also helps reduce light reflected from the bottom of the tank, which keeps the fish calmer and more willing to swim in the open. Active substrates like ADA Amazonia or Fluval Stratum have the added benefit of naturally buffering pH downward, which is a nice bonus for soft-water species like this one.

Is the Exclamation Point Rasbora Right for You?

Before you buy, run through this honest checklist. The Exclamation Point Rasbora is a great fish for the right keeper, but it is not for everyone.

• You have a dedicated nano tank (5-10 gallons) where tiny fish are the stars
• You can use sponge filtration or intake guards. standard filters will eat these fish
• You want one of the smallest fish in the freshwater hobby
• You can keep a group of 12+ for visible schooling behavior
• Your tank has no fish large enough to eat a 0.8-inch adult
• You enjoy the challenge and reward of keeping micro species

Tank Mates

The exclamation point rasbora is a peaceful, non-aggressive nano fish that should only be housed with other small, gentle species. At 0.8 inches (2 cm) max, anything with a mouth big enough to eat them is a threat. The best communities pair them with other micro fish and small invertebrates that share similar water requirements.

Best Tank Mates

• Chili rasboras — same genus, same care requirements, stunning mixed school of Boraras
• Dwarf rasboras — another Boraras species that shares identical water preferences
• Pygmy corydoras — tiny, peaceful bottom dwellers that won’t compete for space
• Habrosus corydoras — another micro cory that stays small and sticks to the bottom
• Otocinclus catfish — gentle algae eaters that ignore nano fish entirely
• Ember tetras — similar size, peaceful temperament, and preference for soft water
• Celestial pearl danios — small, peaceful, and visually complementary
• Neocaridina shrimp (cherry shrimp) — excellent tank mates that add color and help clean up
• Amano shrimp — peaceful algae eaters, though much larger than the fish
• Malaysian trumpet snails — help aerate substrate and clean up uneaten food
• Nerite snails — excellent algae grazers that won’t bother any fish

Tank Mates to Avoid

• Angelfish — way too large and will absolutely eat exclamation point rasboras
• Bettas — can be aggressive and the rasboras may become targets, especially in smaller tanks
• Tiger barbs — fin nippers that are far too active and boisterous for tiny Boraras
• Gourami species (except sparkling gouramis) — most are too large and may prey on or stress nano fish
• Cichlids — even small cichlids like rams can be territorial enough to harass or eat these micro fish
• Large catfish — anything that could fit a rasbora in its mouth is a no-go

Food & Diet

The exclamation point rasbora is an omnivore with a strong micropredator streak — in the wild, it feeds primarily on tiny invertebrates, insect larvae, zooplankton, and other microscopic organisms. In the aquarium, the key thing to remember is that this fish has a very small mouth. Standard-sized flakes and pellets are too big. You need to either crush them into a fine powder or use foods specifically designed for micro fish.

A good staple diet includes crushed high-quality flakes or micro pellets like Hikari Micro Pellets. Supplement regularly with frozen foods — baby brine shrimp, cyclops, and daphnia are excellent choices that provide variety and enhance coloration. Live foods like vinegar eels, microworms, and live baby brine shrimp are absolute favorites and make great conditioning food if you’re looking to breed them.

Feed small amounts 2 to 3 times daily rather than one big feeding. These tiny fish have fast metabolisms and do better with frequent small meals. Only offer what the school can consume in about 2 minutes per feeding. Overfeeding is easy to do with nano fish because the food-to-fish size ratio is so different from what most hobbyists are used to.

Breeding & Reproduction

Breeding Difficulty

Moderate. Exclamation point rasboras will spawn in a well-maintained aquarium without much intervention, but successfully raising the fry is the real challenge. The eggs and fry are extremely tiny, and the adults will eat their own eggs and young if given the chance. Deliberate breeding requires some planning and a dedicated setup.

Spawning Tank Setup

Set up a small breeding tank of 2.5 to 5 gallons (10 to 19 liters) with very gentle filtration — a small air-driven sponge filter turned down low is ideal. Fill the bottom with dense clumps of Java moss, spawning mops, or other fine-leaved plants that give the eggs somewhere to fall where the adults can’t easily reach them. Some breeders use a layer of glass marbles or mesh on the bottom to let eggs drop through to safety.

Keep lighting dim or cover the sides of the tank. These fish naturally spawn in shaded, heavily vegetated areas, and subdued conditions help encourage spawning behavior.

Water Conditions for Breeding

Breeding pairs or groups do best in slightly warmer, softer, and more acidic water than normal care parameters:

• Temperature: 78 to 82°F (26 to 28°C)
• pH: 5.0 to 6.0
• Hardness: 1 to 3 dGH

Using RO water or very soft water mixed with a small amount of tap water works well. Adding Indian almond leaves or peat extract to the breeding tank helps lower pH naturally and adds beneficial tannins. The slight shift toward warmer, softer, more acidic conditions signals to the fish that conditions are right for spawning.

Conditioning & Spawning

Condition a small group (2 to 3 pairs) with frequent feedings of live and frozen foods — baby brine shrimp, daphnia, and microworms are all excellent. After a week or two of conditioning, well-fed females will become noticeably plumper with eggs, and males will display more intensely.

Spawning typically happens in the early morning hours. The fish scatter small, non-adhesive eggs among fine-leaved plants or let them fall to the substrate. A female may release anywhere from 10 to 30 eggs per spawning event. Spawning can be easy to miss because the fish are so small and the behavior is subtle — you may not realize spawning has occurred until you spot tiny fry clinging to the glass a few days later.

Egg & Fry Care

Remove the adults after spawning or rely on the dense plant cover and marbles to protect the eggs. The adults will eat any eggs and fry they can find. Eggs typically hatch in 24 to 48 hours depending on temperature. The fry are absolutely minuscule and will remain attached to plants or glass, absorbing their yolk sac for the first 2 to 3 days.

Once free-swimming, the fry need extremely small first foods. Infusoria, paramecium cultures, or commercially available liquid fry food are essential for the first week or two. After that, you can transition to vinegar eels, microworms, and eventually newly hatched baby brine shrimp as the fry grow. Keep the water very clean with small, frequent water changes using matched parameters. Fry are light-sensitive in the early stages, so keep the breeding tank dimly lit.

In heavily planted, well-established tanks with lots of microorganism growth, some fry may survive without intervention — but deliberate breeding with a dedicated setup will give you much better results. Most exclamation point rasboras in the trade are wild-caught, so captive breeding is a worthwhile endeavor that helps reduce pressure on wild populations.

Common Health Issues

Ich (White Spot Disease)

Ich is the most common disease you’ll encounter with any freshwater fish, and exclamation point rasboras are no exception. Look for small white spots on the body and fins, along with flashing (rubbing against objects) and clamped fins. Treat with a gradual temperature increase to 82 to 84°F (28 to 29°C) combined with a half-dose ich medication — these are small, delicate fish and full-strength treatments can be harsh on them. Prevention is the best approach: quarantine new fish and plants before adding them to your display tank.

Bacterial Infections

Poor water quality is the primary driver of bacterial infections in nano fish. Fin rot, mouth fungus, and general bacterial infections can set in quickly when ammonia, nitrite, or nitrate levels spike — and in a small tank, parameters can deteriorate fast. Regular water changes, proper filtration, and avoiding overcrowding are your best defenses. If you spot red streaks, frayed fins, or cotton-like growths, isolate affected fish and treat with an appropriate antibiotic.

Internal Parasites

Wild-caught exclamation point rasboras can sometimes carry internal parasites that cause weight loss, hollow belly, and faded coloration despite regular feeding. If newly purchased fish seem to eat but never gain weight, internal parasites may be the culprit. A medicated food containing praziquantel or levamisole can help. Quarantining all new arrivals for 2 to 4 weeks before adding them to your main tank is the single best prevention measure.

Common Mistakes to Avoid

• Keeping too few — a group of 3 or 4 will be stressed and hide constantly. These are schooling fish that need at least 8, and 10 to 15 is better. A proper school is more confident, more active, and shows significantly better coloration.
• Using food that’s too large — standard flakes and pellets won’t work. Crush everything into a fine powder or use micro-sized foods. If the food doesn’t fit in their mouth, they simply won’t eat it, and it’ll just rot and foul the water.
• Too much current — powerful filters blast these tiny fish around the tank. A gentle sponge filter is all you need. If you notice your rasboras constantly hiding or struggling to swim, the flow is too strong.
• Skipping the quarantine — since many exclamation point rasboras are wild-caught, they can carry parasites or diseases. Always quarantine new arrivals for 2 to 4 weeks before adding them to an established tank.

Where to Buy

The exclamation point rasbora is the most widely available Boraras species, which is great news if you’ve had trouble finding other members of the genus. You’ll occasionally find them at well-stocked local fish stores, but online retailers are your most reliable bet for healthy specimens.

Flip Aquatics is a great source for nano fish and often carries Boraras species. Dan’s Fish is another excellent option with a solid reputation for quality freshwater fish. Both ship live fish directly to your door.

Expect to pay around $3 to $5 per fish, depending on the source and whether they’re wild-caught or captive-bred. Since you need a group of at least 8 to 10, budget for picking up the whole school at once — it’s better for the fish and usually more cost-effective with shipping.

Frequently Asked Questions

How many exclamation point rasboras should be kept together?

A minimum of 8 is recommended, but 10 to 15 is ideal. Like all Boraras species, these are schooling fish that feel more secure, display better color, and exhibit more natural behavior in larger groups. A school of 3 or 4 will be stressed, pale, and spend most of their time hiding.

What size tank does an exclamation point rasbora need?

A 5-gallon (19-liter) tank is the minimum for a small school. For a larger group of 15 or more, a 10-gallon (38-liter) tank is more appropriate. These are true nano fish that don’t need large tanks, but they do need enough space for a proper school with room for plants and decorations.

Are exclamation point rasboras easy to care for?

Yes, they’re one of the easier Boraras species to keep. They’re more tolerant of moderate water conditions than some of their relatives, and their care requirements are straightforward — soft-ish water, gentle filtration, small foods, and a planted tank. The main things to watch are using appropriately small food and keeping the water stable.

Can exclamation point rasboras live with shrimp?

Absolutely. Cherry shrimp, Amano shrimp, and other dwarf shrimp are some of the best tank mates for this species. The rasboras are too small to bother adult shrimp, and they share the same preference for planted tanks with gentle filtration. The only caveat is that newborn shrimplets may occasionally be eaten, but in a well-planted tank, enough will survive to sustain the colony.

Why is my exclamation point rasbora losing color?

The most common reasons for color loss are stress, hard or alkaline water, bright lighting, and poor diet. Check your water parameters first — these fish color up best in soft, acidic water. Make sure the lighting isn’t too harsh (add floating plants for shade) and that you’re feeding appropriately sized, varied foods. A dark substrate also makes a big difference in how vivid the colors appear.

Can exclamation point rasboras live with bettas?

It’s generally not recommended. While some peaceful bettas might coexist with them, the risk isn’t worth it. Bettas can be unpredictable, and exclamation point rasboras are tiny enough to be harassed or even eaten. If you want to try it, you’d need at least a 10-gallon planted tank with plenty of cover, but there are better tank mate options for both species.

How long do exclamation point rasboras live?

With proper care, exclamation point rasboras live 3 to 5 years in captivity. Stable water conditions, a varied diet, low stress, and keeping them in a proper school all contribute to a longer, healthier lifespan. Sudden parameter swings and poor water quality are the biggest lifespan-shortening factors.

How the Exclamation Point Rasbora Compares to Similar Species

Exclamation Point Rasbora vs. Phoenix Rasbora

The Phoenix Rasbora is slightly larger and much more colorful. If you want maximum visual impact in a nano tank, the Phoenix Rasbora is the better choice. The Exclamation Point Rasbora is for the keeper who appreciates tiny, delicate fish and wants something truly micro.

Exclamation Point Rasbora vs. Neon Green Rasbora

The Neon Green Rasbora is slightly larger and easier to see in a tank. The Exclamation Point Rasbora is the more extreme nano species. Both need stable conditions and groups. For most nano keepers, the Neon Green Rasbora is more practical.

Closing Thoughts

The exclamation point rasbora is one of the best entry points into the world of Boraras nano fish. It’s the most widely available species in the genus, it’s slightly more tolerant of water conditions than some of its relatives, and that exclamation point marking is genuinely one of the coolest patterns in the nano fish world. Set up a planted 5 or 10-gallon tank with dark substrate, soft water, some Indian almond leaves, and a school of 10 to 15 of these little guys — you’ll have a setup that rivals tanks ten times its size for visual impact.

If you’re exploring other rasbora and danio species, check out our care guides for the dwarf rasbora, chili rasbora, and emerald dwarf rasbora. Have you kept exclamation point rasboras? Share your experience in the comments below!

Recommended Video

Check out our rasbora video for more on these amazing nano fish, including the exclamation point rasbora:

References

• Boraras urophthalmoides (Kottelat, 1991) — FishBase
• Boraras urophthalmoides Profile — Seriously Fish
• Exclamation Point Rasbora — Practical Fishkeeping
• Kottelat, M. (1993). “Diagnoses of two new genera and three new species of small fishes from Thailand.” — Ichthyological Exploration of Freshwaters, 4(4): 313-320.

Table of Contents

• Key Takeaways
• Species Overview
• Classification
• Origin & Natural Habitat
• Appearance & Identification
• Average Size & Lifespan
• Care Guide
• Tank Mates
• Food & Diet
• Breeding & Reproduction
• Common Health Issues
• Common Mistakes to Avoid
• Where to Buy
• Frequently Asked Questions
• Closing Thoughts
• Recommended Video
• References
• What Most Care Guides Get Wrong
• Is the Strawberry Rasbora Right for You?
• Species Comparison

The strawberry rasbora is one of those fish that makes you do a double take. At barely over half an inch long, it’s one of the smallest aquarium fish you can buy, and yet it packs a surprising amount of color into that tiny body. These miniature rasboras from the peat swamps of southern Thailand have been gaining serious traction in the nano tank hobby, and for good reason.

But here’s the thing, keeping strawberry rasboras isn’t quite as simple as dropping them into any community tank. Their extremely small size and preference for soft, acidic water mean they need a more specialized setup than your average beginner fish. In my 25+ years in the hobby, I’ve seen too many people lose these little guys because they treated them like just another rasbora. They’re not. Get the group size, the water, and the tank size right – or skip this fish.

What Most Care Guides Get Wrong About Strawberry Rasbora

The most common mistake with Strawberry Rasboras is keeping them in groups that are too small. These fish genuinely need eight to twelve to show natural schooling behavior. In my experience working with rasboras at the stores I managed, small groups of three or four spend all their time hiding.

Key Takeaways

• One of the smallest aquarium fish: maxes out at just 0.6 inches (1.5 cm), making it a true micro fish
• Requires very soft, acidic water: pH 4.0-6.5, which rules out most standard community setups
• Best kept in a species-only nano tank: a 5-gallon minimum, but 10 gallons gives you much more room to work with
• Peaceful but extremely delicate: tank mate options are very limited due to size
• Not a beginner fish: demands stable water chemistry and carefully managed conditions

Species Overview

Field	Details
Scientific Name	Boraras naevus
Common Names	Strawberry Rasbora
Family	Danionidae
Origin	Southern Thailand (peat swamp forests)
Care Level	Moderate to Advanced
Temperament	Peaceful
Diet	Omnivore (micro foods)
Tank Level	Mid
Maximum Size	0.6 inches (1.5 cm)
Minimum Tank Size	5 gallons (19 liters)
Temperature	68-79°F (20-26°C)
pH	4.0-6.5
Hardness	1-5 dGH
Lifespan	3-5 years in captivity
Breeding	Egg scatterer
Breeding Difficulty	Moderate to Difficult
Compatibility	Species-only or carefully selected nano tank mates
OK for Planted Tanks?	Yes

Classification

Taxonomic Level	Classification
Order	Cypriniformes
Family	Danionidae
Subfamily	Rasborinae
Genus	Boraras
Species	B. naevus (Conway & Kottelat, 2011)

The genus Boraras is a small group of miniature cyprinids containing only six described species, all native to Southeast Asia. The genus name is an anagram of Rasbora, the genus these fish were originally assigned to. All Boraras species are among the smallest freshwater fish in the world, and they share a preference for soft, acidic blackwater habitats.

The species name “naevus” comes from the Latin word for “blemish” or “birthmark,” referring to the prominent dark spot on the body that is a key identifying feature. Boraras naevus was formally described relatively recently in 2011 by Conway and Kottelat, making it one of the newest additions to the genus.

Origin & Natural Habitat

The strawberry rasbora is found exclusively in southern Thailand, specifically in the provinces around the Malay Peninsula region. Their native habitat is peat swamp forests, a type of environment that’s becoming increasingly rare due to agricultural development and deforestation across Southeast Asia.

These peat swamps are unlike anything most aquarists picture when they think of a fish’s natural home. The water is extremely shallow, often just a few inches deep, and stained a deep brown or black from the massive amounts of decomposing leaf litter and organic material on the forest floor. Sunlight barely penetrates the canopy above, keeping the water dimly lit and cool relative to other tropical habitats.

The water chemistry in these swamps is extreme by aquarium standards. We’re talking a pH that can drop below 4.0, that’s roughly as acidic as orange juice. Mineral content is virtually nonexistent, with general hardness often at or near zero. The substrate is a thick mat of fallen leaves, peat, and decaying plant material. There’s very little aquatic vegetation growing in the water itself, but the structure from roots, branches, and leaf litter is dense.

Understanding this habitat is crucial to keeping strawberry rasboras successfully. These aren’t fish that evolved in clean, neutral water with lots of current. They come from still, tannin-rich blackwater conditions that most fishkeepers would consider extreme.

Appearance & Identification

Despite being almost impossibly small, the strawberry rasbora is a genuinely attractive fish. The base body color ranges from a warm reddish-orange to a deep strawberry pink, which, naturally, is where the common name comes from. The intensity of this color varies depending on the fish’s condition, diet, and water quality, but a healthy specimen in good water is surprisingly vibrant for something half an inch long.

The most distinctive feature is the dark blotch or spot on the middle of the body, which is the “naevus” (blemish) the species is named for. This spot is typically oval-shaped and quite prominent relative to the fish’s tiny size. There may also be a smaller dark spot near the base of the tail fin. The overall body shape is slender and somewhat elongated for a cyprinid.

The fins are mostly transparent with a slight reddish tint, especially the caudal (tail) fin. Under the right conditions, soft, acidic water with tannins and subdued lighting, the red-orange coloration deepens significantly, and the fish practically glow against a dark background.

It’s worth noting that strawberry rasboras can look quite different depending on their environment. In hard, alkaline water under bright lights, they’ll appear pale and washed out. Put them in the blackwater conditions they evolved in, and it’s like looking at a completely different fish.

Male vs. Female

Sexing strawberry rasboras is tricky given their minuscule size, but there are a few differences you can spot in mature specimens. Females tend to be slightly rounder in the belly, particularly when carrying eggs, and may appear marginally larger overall. Males are slimmer with a slightly more intense red-orange coloration, especially during courtship. These differences are subtle, though, you’ll often need a magnifying glass and good lighting to tell them apart with any confidence.

Average Size & Lifespan

The strawberry rasbora maxes out at around 0.6 inches (1.5 cm) in total length. To put that in perspective, a fully grown adult is barely larger than a grain of rice. This makes it one of the smallest freshwater aquarium fish available in the hobby, only a handful of species are comparably tiny.

Despite their almost unbelievably small size, strawberry rasboras can live 3 to 5 years with proper care. That’s a respectable lifespan for a fish this small. The key to reaching the upper end of that range is maintaining the stable, soft, acidic water conditions they need and providing a stress-free environment without oversized or aggressive tank mates.

Care Guide

Tank Size

A 5-gallon (19-liter) tank is the minimum for a small group of strawberry rasboras, but I’d recommend starting with a 10-gallon (38-liter) tank if you can. Here’s why: the bigger challenge with these fish isn’t swimming space, it’s water stability. A 5-gallon tank is extremely sensitive to parameter swings, and strawberry rasboras need rock-solid water chemistry. A 10-gallon tank gives you a much larger margin for error, and the extra water volume makes it easier to maintain those low pH and hardness levels consistently.

Keep at least 8-10 individuals. Even though they’re tiny, they’re a shoaling species that feels much more secure in larger groups. In a school of fewer than 6, they’ll spend most of their time hiding and you’ll barely see them.

Water Parameters

Parameter	Ideal Range
Temperature	68-79°F (20-26°C)
pH	4.0-6.5
Hardness	1-5 dGH
KH	0-2 dKH

This is where strawberry rasboras get demanding. That pH range of 4.0-6.5 is not a typo, these fish genuinely come from some of the most acidic freshwater habitats on the planet. Most community tank setups run a pH of 7.0 or higher, which is well outside what strawberry rasboras can tolerate long-term.

To achieve these conditions, you’ll likely need to use RO (reverse osmosis) water or very soft tap water remineralized to minimal levels. Indian almond leaves, peat moss, alder cones, and driftwood all help lower pH naturally while releasing beneficial tannins. Some keepers use peat filtration or commercially available blackwater extracts to maintain the acidic conditions these fish require.

Temperature-wise, they actually prefer slightly cooler water than many tropical fish. A range of 72-76°F (22-24°C) is ideal for everyday keeping. They can handle warmer temperatures up to 79°F (26°C), but they seem most active and colorful in the lower to middle part of their range.

Filtration & Water Flow

Very gentle filtration is essential. Remember, these fish come from nearly still peat swamps, any significant current will exhaust them and cause chronic stress. A small sponge filter is the gold standard here. It provides biological filtration, creates minimal flow, and is safe for both adults and any fry that might appear.

If you’re using a hang-on-back or internal filter, baffle the output significantly. These are half-inch fish, even moderate flow will push them around. Water changes should be small and frequent. Aim for 10-15% weekly, using pre-conditioned water that matches the tank’s temperature and chemistry as closely as possible. Large water changes with parameter swings are one of the fastest ways to lose strawberry rasboras.

Lighting

Dim lighting is strongly preferred. In the wild, the dense canopy above peat swamp forests blocks most sunlight, and the tannin-stained water absorbs whatever light does get through. Strawberry rasboras are most comfortable and show their best colors under subdued lighting conditions.

Floating plants are your best friend here. Salvinia, Amazon frogbit, dwarf water lettuce, or red root floaters all do a great job of diffusing overhead light while adding a natural feel. If you’re running a planted tank, use low-light species that don’t require intense illumination, this keeps both the plants and the fish happy.

Plants & Decorations

Dense planting is highly recommended. Java moss, Cryptocoryne species (which thrive in acidic water), Java fern, and Bucephalandra all work well in the low-pH conditions strawberry rasboras need. Create plenty of hiding spots with dense plant clusters, but leave some open swimming space in the center or front of the tank.

Driftwood is practically mandatory. It provides structure, releases tannins that help maintain acidity, and creates the type of natural cover these fish feel secure around. Go heavy on the botanicals, dried Indian almond leaves (catappa leaves), alder cones, and seed pods on the substrate replicate their natural peat swamp habitat beautifully. As a bonus, decomposing leaves support colonies of microorganisms that strawberry rasboras will graze on throughout the day.

Substrate

A dark, fine-grained substrate works best. Dark sand or an active planted tank substrate (which can help buffer pH lower) are both good choices. The dark background makes the reddish-orange coloration of the fish pop dramatically. Avoid anything sharp or coarse, these are incredibly delicate fish with tiny mouths that may pick at the substrate surface.

A layer of dried leaves over the substrate adds another layer of authenticity and function. The leaves provide cover, tint the water, and become a feeding ground for the microfauna that strawberry rasboras snack on between meals.

Tank Mates

Best Tank Mates

Let me be direct here: a species-only tank is the safest and easiest approach for strawberry rasboras. At 0.6 inches (1.5 cm), these fish are small enough to be eaten by almost anything with a mouth big enough to fit them. Even “peaceful” community fish like neon tetras can be a threat to something this tiny.

That said, if you want to add some diversity, here are the only tank mates I’d consider:

• Other Boraras species: chili rasboras (B. brigittae), least rasboras (B. urophthalmoides), and exclamation point rasboras (B. urophthalmoides) are similar in size and share the same water requirements
• Small Corydoras species: pygmy corydoras (Corydoras pygmaeus) and dwarf corydoras (C. hastatus) are gentle enough and stay small
• Otocinclus catfish: peaceful algae eaters that ignore tiny fish entirely
• Small shrimp: neocaridina shrimp (cherry shrimp) or caridina shrimp (crystal reds, if your water is soft enough, which it likely will be)
• Small snails: nerite snails, ramshorn snails, and Malaysian trumpet snails are all safe choices

Tank Mates to Avoid

• Most tetras: even small species like neon tetras are large enough to bully or eat strawberry rasboras
• Bettas: too large and too likely to view them as food
• Any cichlid: even dwarf cichlids like Apistogramma will happily snack on fish this small
• Barbs of any size: too active, too large, and too nippy
• Larger rasboras: harlequin rasboras and similar species are giants by comparison
• Gouramis: even small species like sparkling gouramis may prey on them
• Any fast-moving or aggressive species: strawberry rasboras will be outcompeted for food and stressed constantly

Food & Diet

Feeding strawberry rasboras requires some adjustment from how you’d feed most aquarium fish. Their mouths are extraordinarily small, we’re talking about a fish that’s barely half an inch long. Standard flake food is simply too large for them to eat unless it’s been crushed into a fine powder.

The best staple foods are micro-sized options: micro pellets designed for nano fish, finely crushed high-quality flake food, or powdered foods like Hikari First Bites. These should be small enough for their tiny mouths to handle.

Where strawberry rasboras really shine is with live and frozen micro foods. Vinegar eels, microworms, Walter worms, Grindal worms, baby brine shrimp (BBS), cyclops, and daphnia nauplii are all excellent choices. Live foods trigger a strong feeding response and help bring out the best coloration. If you can culture your own live foods, you’ll see a noticeable difference in how vibrant and active these fish become.

Feeding frequency: Feed small amounts once or twice daily. Only offer what they can consume in about a minute. Overfeeding in a small nano tank fouls the water rapidly, and deteriorating water quality is one of the biggest threats to these sensitive fish.

Pro tip: A well-established tank with plenty of leaf litter and botanicals will develop biofilm and microfauna colonies that strawberry rasboras graze on throughout the day. This supplemental natural food source is one of the reasons a mature, heavily planted tank works so much better for these fish than a newly set up one.

Is the Strawberry Rasbora Right for You?

Before you add a Strawberry Rasbora to your tank, here is an honest assessment of what you’re signing up for. I’d rather you know exactly what to expect now than find out the hard way after you’ve already bought one.

• Experience level: Strawberry Rasboras are best suited for intermediate to advanced keepers. They have specific requirements that can overwhelm beginners.
• Tank size commitment: You’ll need at least 10 gallons, though bigger is always better. Make sure you have room for the tank before buying.
• Tank mate planning: Strawberry Rasboras can be territorial, so plan your community carefully. Not every fish will work as a tank mate.
• Maintenance demands: Expect regular water testing and consistent water changes. Strawberry Rasboras are sensitive to parameter fluctuations.
• Cost to keep: Strawberry Rasboras are reasonably affordable. Standard equipment and quality food cover most needs.
• Time investment: Beyond daily feeding and weekly maintenance, regular observation is the best way to catch health issues early.
• Long-term commitment: With proper care, Strawberry Rasboras can live up to 5 years. Make sure you’re ready for years of consistent care.

Breeding & Reproduction

Strawberry rasboras are egg scatterers, and while breeding them is possible in captivity, it requires some patience and attention to detail.

Breeding Difficulty

Moderate to difficult. They’ll spawn readily enough in the right conditions, but raising the fry is where the real challenge lies. The eggs and fry are microscopic, and the adults will eat both eggs and fry if given the opportunity.

Spawning Tank Setup

A small breeding tank of 2.5-5 gallons (10-19 liters) works well. Fill the bottom with clumps of Java moss or fine-leaved plants like Taxiphyllum species, which give the eggs somewhere to land where the adults can’t easily reach them. Keep the tank dimly lit, both eggs and fry are very light-sensitive.

A bare-bottom tank with a mesh divider works as an alternative. The mesh should be fine enough to let eggs fall through but prevent adults from reaching them below.

Water Conditions for Breeding

The breeding tank water should match their preferred acidic conditions closely. Aim for a pH of 5.0-6.0, temperature around 76-79°F (24-26°C), and near-zero hardness. Use RO water with peat filtration or Indian almond leaf extract to achieve these parameters. An air-powered sponge filter set to the gentlest possible flow is all the filtration you need.

Conditioning & Spawning

Condition breeding pairs or small groups with plenty of live foods, baby brine shrimp, microworms, and daphnia nauplii are ideal. When females are visibly plump with eggs, introduce a conditioned pair or a small group (2-3 males, 2-3 females) into the spawning tank. Spawning typically occurs in the morning. Boraras species tend to scatter small numbers of eggs among plants over several days rather than producing a single large spawn event.

Egg & Fry Care

Remove the adults after spawning is observed, as they will eat any eggs and fry they find. Eggs are extremely small and may take 24-48 hours to hatch. The fry are absolutely minuscule, you’ll need a magnifying glass to even see them in the first few days.

Feed the fry infusoria, paramecium, or commercially available liquid fry food for the first 1-2 weeks. Once they’re large enough (which takes a while given the tiny starting size), graduate to vinegar eels, microworms, and eventually freshly hatched baby brine shrimp. Growth is slow, don’t expect them to reach adult size for several months. Keep the rearing tank dim and maintain pristine water quality with very gentle, frequent water changes.

Common Health Issues

Strawberry rasboras are generally healthy fish when kept in proper conditions, but their tiny size makes them fragile when things go wrong. Problems tend to escalate quickly in small bodies.

pH Shock & Osmotic Stress

This is the number one killer of strawberry rasboras. Because they require such extreme water conditions (very low pH, near-zero hardness), any sudden shift in water chemistry can be fatal. Moving them from soft, acidic water to harder, more alkaline conditions, or vice versa, causes osmotic stress that these tiny fish simply can’t recover from. Always acclimate new arrivals extremely slowly, using drip acclimation over 1-2 hours minimum.

Ich (White Spot Disease)

Strawberry rasboras can contract ich, especially during the stress of transport and acclimation to a new tank. The white spots are visible even on such a small fish. Treatment requires caution, these are sensitive fish, so use half-dose medications or, better yet, raise the temperature gradually to 82°F (28°C) and add a small amount of aquarium salt (if the low pH allows it). Some keepers prefer heat treatment alone for Boraras species.

Internal Parasites

Wild-caught strawberry rasboras may carry internal parasites. Symptoms include a sunken belly, lethargy, and loss of color despite good water conditions. Quarantining new arrivals for at least two weeks is essential. Treat suspected cases with food soaked in an anti-parasitic medication, using the smallest effective dose.

General Prevention

Prevention is everything with strawberry rasboras. Quarantine all new fish, maintain stable water parameters (stability matters even more than hitting exact numbers), and avoid overfeeding. Indian almond leaves and other botanicals in the tank release mild antifungal and antibacterial compounds that help keep these fish healthy naturally. The tannin-rich water they prefer is actually mildly antimicrobial, another reason to embrace the blackwater approach.

Common Mistakes to Avoid

• Putting them in a standard community tank: This is the most common mistake by far. Strawberry rasboras are not community fish. They’re too small, too fragile, and need water chemistry that most community fish can’t tolerate. A species-only nano setup or a tank with only the smallest, gentlest tank mates is the way to go.
• Ignoring water chemistry: You cannot keep these fish in hard, alkaline tap water and expect them to survive long-term. They need soft, acidic conditions. If your tap water is hard, you’ll need RO water or another method to bring the parameters in line.
• Keeping too few: A group of 3-4 strawberry rasboras will be shy, stressed, and constantly hiding. Get at least 8-10 to see natural shoaling behavior and confident, colorful fish.
• Large water changes with mismatched parameters: A 50% water change in a nano tank with water that’s even slightly different in pH or temperature can be catastrophic. Stick to small, frequent changes with pre-conditioned, matched water.
• Feeding standard-sized food: Regular flake food is too large. You need micro-sized foods or finely crushed alternatives. Live micro foods are the gold standard.
• New tank syndrome: Setting up a brand new tank and immediately adding strawberry rasboras is a recipe for disaster. These fish do much better in mature, established tanks with stable biology and natural biofilm to graze on.

Where to Buy

Strawberry rasboras are not as widely available as some of the more common Boraras species like chili rasboras, but they do appear in the hobby through specialty retailers and online sellers. You’re unlikely to find them at big box pet stores, this is a fish you’ll need to source from dedicated aquarium shops or order online.

I recommend checking Flip Aquatics and Dan’s Fish for availability. Both specialize in quality freshwater fish and are reliable sources for nano species like Boraras. When ordering, be aware that shipping tiny, sensitive fish in extreme temperatures (summer heat or winter cold) carries additional risk. Time your orders for mild weather when possible, and opt for overnight or express shipping.

Expect to pay a bit more per fish than you would for common rasboras, typically $4-8 per fish depending on the source and availability. Buy a group of 8-10 at once rather than adding them one or two at a time.

Frequently Asked Questions

How many strawberry rasboras should be kept together?

A minimum of 8-10 is recommended, though more is always better. Strawberry rasboras are a shoaling species that become visibly stressed, shy, and pale in small groups. In a proper school of 10+, they feel secure, display bolder colors, and engage in fascinating natural behaviors including sparring displays between males.

What size tank does a strawberry rasbora need?

A 5-gallon (19-liter) tank is the minimum, but a 10-gallon (38-liter) tank is strongly preferred. The extra water volume provides much better parameter stability, which is critical for a species that requires very specific and extreme water chemistry. The larger tank also gives you room for a school of 10+ without overcrowding.

Are strawberry rasboras good for beginners?

No, not really. While they’re peaceful and don’t require a large tank, their need for very soft, acidic water (pH 4.0-6.5) and their extreme sensitivity to parameter changes make them a poor choice for someone new to the hobby. They’re best suited for intermediate to advanced keepers who are comfortable working with RO water, botanicals, and maintaining stable nano tank conditions.

Can strawberry rasboras live with shrimp?

Yes, adult neocaridina (cherry) shrimp are safe with strawberry rasboras. The fish are too small to eat adult shrimp, and both species are peaceful. If your water is very soft and acidic, caridina shrimp like crystal reds may actually be a better match since they prefer similar conditions. Baby shrimp (shrimplets) are likely safe too, given how small the rasboras’ mouths are.

What’s the difference between strawberry rasboras and chili rasboras?

Both are Boraras species of similar size, but they’re distinct species with different markings. Chili rasboras (Boraras brigittae) have a dark lateral stripe running along the body with a red stripe above it, while strawberry rasboras (Boraras naevus) have a prominent dark spot (blotch) on the body rather than a stripe. Chili rasboras are from Borneo, while strawberry rasboras are from southern Thailand. Care requirements are similar for both species.

Do strawberry rasboras need a heater?

It depends on your room temperature. Strawberry rasboras tolerate a temperature range of 68-79°F (20-26°C), which is cooler than many tropical fish. If your home stays consistently above 68°F (20°C), you may not need a heater. However, a small adjustable heater set to the low-to-mid 70s provides stability and prevents dangerous overnight temperature drops, especially in a small nano tank that loses heat quickly.

Why are my strawberry rasboras hiding all the time?

The most common causes are too few fish in the group, inadequate cover, or overly bright lighting. Strawberry rasboras need a school of at least 8-10 to feel secure. Make sure the tank has plenty of plants, floating plants to dim the light, and botanical cover like leaves and driftwood. Also check for aggressive tank mates, even a single fish that’s too large or active can keep the entire school in hiding.

How the Strawberry Rasbora Compares to Similar Species

If you’re considering a Strawberry Rasbora, you’ve probably also looked at the Chili Rasbora. Both fill similar roles, but the differences matter when planning your tank. The Strawberry Rasbora has its own distinct personality and care needs. In my experience, the choice often comes down to the specific community you’re building and whether your water parameters favor one over the other.

The Dwarf Rasbora is worth considering as well. While the Strawberry Rasbora and the Dwarf Rasbora share some overlap in care, they bring different energy to a tank. If you have the space, keeping both in separate setups gives you a great chance to compare their behavior firsthand.

Closing Thoughts

The strawberry rasbora is a specialist fish for a specialist setup, and that’s part of what makes it so rewarding. Building a blackwater nano tank around these micro fish is a genuinely different experience from maintaining a standard community aquarium. When you get the conditions right and see a school of 10+ strawberry rasboras swimming through tannin-stained water over a carpet of leaf litter, glowing that deep strawberry red, it’s something special.

They’re not for everyone, and they’re definitely not a fish you should impulse-buy without doing your homework first. But if you’re willing to put in the effort to create the acidic, soft-water environment they need, strawberry rasboras will reward you with a school that glows. That’s not an exaggeration – a group of 12 in the right water, over dark substrate, under dim lighting, is one of the best things you can do with a 10-gallon.

If you’re interested in other nano rasbora species, check out our Rasboras & Danios species directory for more care guides on Boraras and other small rasbora species.

Recommended Video

Check out our rasbora species video for an overview of some of the best rasboras in the hobby, including the strawberry rasbora:

References

• Boraras naevus Profile – Seriously Fish
• Boraras naevus (Conway & Kottelat, 2011) – FishBase
• Boraras: The World’s Tiniest Aquarium Fish – Practical Fishkeeping
• Boraras naevus – The Aquarium Wiki

Table of Contents

• What Care Guides Get Wrong
• Key Takeaways
• Species Overview
• Classification
• Origin & Natural Habitat
• Appearance & Identification
• Average Size & Lifespan
• Care Guide
• Is It Right for You?
• Tank Mates
• Food & Diet
• Breeding & Reproduction
• Common Health Issues
• Common Mistakes to Avoid
• Where to Buy
• Frequently Asked Questions
• Species Comparison
• Closing Thoughts
• Recommended Video
• References

The brilliant rasbora is one of those fish that’s been quietly available in the hobby for decades, but it never quite got the spotlight it deserves. It’s overshadowed by flashier species like the harlequin rasbora or the chili rasbora, yet if you’ve ever seen a school of these in a well-maintained planted tank, you know they hold their own. That bold black lateral stripe paired with the bright red-orange tail is a look that’s simple, clean, and genuinely attractive.

What Most Care Guides Get Wrong About the Brilliant Rasbora

The Brilliant Rasbora is a classic case of a fish that is brilliant in name but only occasionally brilliant in practice. The misconception is that it always looks shiny and metallic. In reality, the iridescence is angle-dependent and lighting-dependent. Under direct LED light, it can look almost plain. With side lighting and a dark background, it genuinely sparkles. The other mistake is keeping them in tanks that are too small. This is a moderately sized rasbora (3-4 inches) that needs swimming room and a proper school.

What makes the brilliant rasbora stand out among rasboras is its size and toughness. At up to 2 inches (5 cm), it’s one of the larger true Rasbora species, which gives it more presence in a community tank than the smaller micro rasboras that dominate the hobby right now. It’s also incredibly hardy and tolerant of a wide range of water conditions, making it an excellent choice for beginners and experienced hobbyists alike. Let me walk you through everything you need to know about keeping this underrated fish.

Key Takeaways

• Minimum tank size is 15 gallons (57 liters) for a school of 6, but a 20-gallon long with 10+ fish really shows off their schooling behavior
• Extremely hardy and adaptable — tolerates pH from 6.0 to 8.0 and a wide hardness range, making it forgiving for beginners
• Peaceful schooling fish — safe with virtually any community tank mate that won’t eat them
• Omnivore — eagerly accepts flakes, pellets, and frozen foods with no fuss
• Also known as the Blackline Rasbora or Red-tailed Rasbora — named for the distinctive black lateral stripe and colorful caudal fin

Species Overview

Field	Details
Scientific Name	Rasbora borapetensis
Common Names	Brilliant Rasbora, Blackline Rasbora, Red-tailed Rasbora
Family	Danionidae
Origin	Thailand, Laos, Cambodia, Malaysia
Care Level	Easy
Temperament	Peaceful
Diet	Omnivore
Tank Level	Mid
Maximum Size	2 inches (5 cm)
Minimum Tank Size	15 gallons (57 liters)
Temperature	72–79°F (22–26°C)
pH	6.0–8.0
Hardness	2–15 dGH
Lifespan	3–5 years in captivity
Breeding	Egg scatterer
Breeding Difficulty	Moderate
Compatibility	Community
OK for Planted Tanks?	Yes

Classification

Taxonomic Level	Classification
Order	Cypriniformes
Family	Danionidae
Subfamily	Rasborinae
Genus	Rasbora
Species	R. borapetensis (Smith, 1934)

The genus Rasbora is one of the largest cyprinid genera, containing dozens of species distributed across Southeast Asia. Unlike many of the smaller “rasboras” that have been reclassified into genera like Trigonostigma, Boraras, and Sundadanio over the years, the brilliant rasbora remains a true Rasbora in the traditional sense.

The species was first described by Hugh McCormick Smith in 1934 from specimens collected in Bung Borapet — a large freshwater swamp lake in Nakhon Sawan Province, Thailand. That’s where the species name borapetensis comes from. It’s a member of the family Danionidae (previously grouped under Cyprinidae in older references), which also includes danios and many other small cyprinids popular in the aquarium hobby.

Origin & Natural Habitat

The brilliant rasbora is native to mainland Southeast Asia, with a range that covers Thailand, Laos, Cambodia, and peninsular Malaysia. It’s most commonly associated with the Mekong and Chao Phraya river basins in Thailand, but populations are found across a broad geographic area.

In the wild, these fish inhabit slow-moving streams, marshes, ponds, and flooded fields. They’re often found in relatively shallow, still or gently flowing water with plenty of aquatic vegetation. Unlike many popular rasbora species that come from blackwater forest streams, the brilliant rasbora tends to occupy more open habitats — rice paddies, irrigation canals, and the margins of larger water bodies. These environments often have neutral to slightly alkaline water, which explains why this species is so adaptable to a wide range of pH levels in captivity.

The substrate in their natural habitat is typically muddy or silty, and vegetation ranges from dense aquatic plants to sparse emergent grasses depending on the season. Southeast Asian freshwater habitats are often subject to significant seasonal changes in water level and flow, so the brilliant rasbora has evolved to handle fluctuating conditions — a trait that translates directly into hardiness in the home aquarium.

Most brilliant rasboras sold in the trade are either wild-caught from Thailand or commercially bred in Asian fish farms. Unlike some rasbora species that are difficult to breed commercially, R. borapetensis breeds readily in captivity.

Appearance & Identification

The brilliant rasbora has a sleek, elongated body shape that’s more streamlined than many of the deeper-bodied rasbora species. The base coloration is a silvery-olive tone across the upper body, fading to a lighter silver-white on the belly. But what really defines this fish visually are two key features: the bold black lateral stripe and the bright red-orange tail.

The black stripe runs along the entire length of the body from the tip of the snout to the base of the caudal fin. It’s clean, well-defined, and immediately catches the eye — this is where the “Blackline Rasbora” common name comes from. Just above this dark stripe, you’ll often notice a thin gold or iridescent line that adds a subtle shimmer, especially when the light catches it at the right angle.

The caudal (tail) fin is where this fish really earns the “brilliant” and “red-tailed” parts of its common names. The base of the tail displays a vivid patch of red, orange, or golden-yellow coloring that contrasts sharply with the black stripe. In healthy, well-kept specimens, this color can be quite intense. The dorsal fin also shows a faint reddish tinge at its base. All other fins are mostly transparent.

Overall, it’s a clean and elegant look. Not as flashy as a neon tetra or a celestial pearl danio, but there’s a classic simplicity to the brilliant rasbora that grows on you. A tight school of 10 or more moving through a planted tank is genuinely striking.

Male vs. Female

Sexing brilliant rasboras isn’t especially difficult once the fish are mature. Females tend to be slightly larger and noticeably fuller-bodied, particularly when carrying eggs — they develop a rounder belly profile that’s easy to spot from above. Males are slimmer and more streamlined, and they often display slightly more intense coloration in the tail fin. The differences are subtle in younger fish but become more apparent as they reach full size.

Average Size & Lifespan

Brilliant rasboras reach a maximum size of about 2 inches (5 cm) in total length, making them one of the larger species in the genus Rasbora commonly kept in aquariums. This extra size compared to micro rasboras like Boraras species gives them more visual presence in a community setup and makes them less vulnerable to predation by slightly larger tank mates.

In captivity, expect a lifespan of 3 to 5 years with proper care. Consistent water quality, a varied diet, and a stress-free environment with enough schooling companions all contribute to reaching the upper end of that range. As with most small cyprinids, genetic quality matters too — buying from reputable sellers tends to result in healthier, longer-lived fish.

Care Guide

Tank Size

A 15-gallon (57-liter) tank is the minimum for a small school of 6 brilliant rasboras, but I’d strongly suggest going with a 20-gallon long if your space and budget allow it. These are active swimmers that appreciate horizontal swimming room, and a longer tank lets a school of 10 or more display natural schooling behavior that’s simply not possible in a smaller footprint.

Because they spend most of their time in the middle water column, a tank with more length and width matters more than height. The 20-gallon long format is ideal — it gives them plenty of room to cruise back and forth while still being manageable for most fishkeepers.

Water Parameters

Parameter	Ideal Range
Temperature	72–79°F (22–26°C)
pH	6.0–8.0
Hardness	2–15 dGH
KH	1–10 dKH

One of the biggest selling points of the brilliant rasbora is its flexibility with water chemistry. That pH range of 6.0 to 8.0 is genuinely broad — you don’t need to chase soft, acidic conditions to keep this fish happy. If your tap water comes out at 7.5 with moderate hardness, the brilliant rasbora will do just fine without any adjustments. That’s a real advantage over species like chocolate gouramis or certain wild-caught rasboras that demand specific water chemistry.

Temperature-wise, they prefer the lower to mid-70s, which is slightly cooler than many tropical fish. This actually makes them a good match for species like white cloud mountain minnows or certain danios that prefer temperatures below 80°F (27°C). As always, stability matters more than hitting a perfect number — keep your parameters consistent and avoid sudden swings.

Filtration & Water Flow

Brilliant rasboras come from slow-moving to still water, so gentle filtration is the way to go. A sponge filter works well for smaller setups and is the safest option if you have fry in the tank. For larger aquariums, a hang-on-back filter or canister filter with a spray bar to diffuse the output will keep things clean without creating too much current.

Weekly water changes of 20–25% are a good baseline. These are relatively low-bioload fish, but regular maintenance keeps nitrates in check and ensures stable conditions. If you’re running a heavily planted tank, the plants will help with nutrient uptake, but that doesn’t replace consistent water changes.

Lighting

The brilliant rasbora isn’t particularly demanding when it comes to lighting. They look good under moderate lighting, which conveniently lines up with what most planted tanks run. Unlike some species that wash out under bright lights, brilliant rasboras maintain their coloring reasonably well across different lighting levels.

That said, they do tend to show more confidence and natural behavior when there are some shaded areas in the tank. Floating plants create dappled light patterns that give the fish zones to retreat to when they want a break from brighter areas. The contrast of light and shadow also makes the black lateral stripe and red tail pop a bit more visually.

Plants & Decorations

A planted tank is the ideal setup for brilliant rasboras. They come from vegetated habitats in the wild, and live plants provide the security and visual barriers that help them feel at home. Java fern, Vallisneria, Cryptocoryne species, and stem plants like Rotala or Hygrophila all work well. Dense planting along the back and sides with open swimming space in the center is a layout that looks great and functions perfectly for this species.

Driftwood and smooth rocks add structure and create natural-looking boundaries in the aquascape. If you want to go for a Southeast Asian biotope look, combine driftwood, Java fern, and a sandy substrate — it’s simple but effective. Indian almond leaves or other dried botanicals can be added for a more natural aesthetic and the mild tannin release, though this species doesn’t require blackwater conditions.

Substrate

Brilliant rasboras aren’t picky about substrate since they spend their time in the mid-water column rather than near the bottom. Fine sand or a quality planted tank substrate both work well. A darker substrate tends to bring out the best coloration in most fish, and the brilliant rasbora is no exception — the black stripe and red tail look sharper against a dark background than over bright white gravel.

If you’re going for a natural biotope look, fine sand or a sand-and-gravel mix mimics the muddy and silty substrates of their native Southeast Asian habitats.

Is the Brilliant Rasbora Right for You?

Before you buy, run through this honest checklist. The Brilliant Rasbora is a great fish for the right keeper, but it is not for everyone.

• You have a 30-gallon or larger tank for a school of 3-4 inch rasboras
• You enjoy iridescent fish that catch the light from different angles
• You can keep a group of 6-8+ for proper schooling
• Your tank has side lighting or angled lighting that shows off iridescence
• You want a peaceful, hardy species for a mid-sized community
• You appreciate a classic rasbora that looks much better in person than in photos

Tank Mates

The brilliant rasbora is a genuinely peaceful fish that gets along with just about anything that won’t try to eat it. Their slightly larger size compared to micro rasboras makes them compatible with a wider range of community fish.

Best Tank Mates

• Corydoras catfish — peaceful bottom dwellers that complement mid-level rasboras perfectly
• Harlequin rasboras — a natural pairing, similar temperament and overlapping native range
• Ember tetras — small, peaceful, and the warm orange tones pair nicely with the brilliant rasbora’s red tail
• Kuhli loaches — gentle bottom dwellers that add activity to the lower tank level
• Cherry barbs — another peaceful Southeast Asian species that works well in the same conditions
• Dwarf gouramis — a colorful centerpiece fish that won’t bother rasboras
• Otocinclus catfish — non-threatening algae eaters perfect for community setups
• Neon and cardinal tetras — the blue tones contrast beautifully with the rasbora’s warm reds
• Cherry shrimp — brilliant rasboras are generally safe with adult shrimp, though very small shrimplets may occasionally be at risk
• White cloud mountain minnows — another hardy, cooler-water species that overlaps well in temperature preference

Tank Mates to Avoid

• Large cichlids — any fish big enough to see a 2-inch rasbora as a snack
• Tiger barbs — too nippy and boisterous for peaceful rasboras
• Angelfish — they may eat brilliant rasboras as they grow larger
• Red tail sharks — territorial and prone to chasing small schooling fish
• Aggressive or highly territorial species — anything that will stress out or outcompete the rasboras for food

Food & Diet

Brilliant rasboras are easy-going omnivores that accept pretty much anything you offer. In the wild, they feed on small insects, worms, crustaceans, and plant matter. In the aquarium, they’ll eagerly take flake food, micro pellets, and freeze-dried options as a daily staple.

To keep them in peak color and health, supplement their base diet with frozen or live foods a few times per week. Daphnia, brine shrimp, bloodworms, and cyclops are all great choices. You’ll notice the red-orange coloring in the tail becomes more vivid when they’re getting a varied, high-quality diet — color-enhancing foods with carotenoids make a real difference.

Feeding frequency: Once or twice daily, in small amounts they can consume within 2–3 minutes. These are active fish, but they have small mouths and stomachs — small, frequent meals are better than one large feeding.

Tip: Brilliant rasboras prefer to eat in the middle water column. Slow-sinking foods or flakes that stay suspended briefly work best. If you’re keeping them with bottom feeders like corydoras, the cories will clean up anything that makes it to the substrate.

Breeding & Reproduction

Brilliant rasboras are egg scatterers that can be bred in captivity, though they require a bit more effort to spawn consistently compared to some of the easier danio species.

Breeding Difficulty

Moderate. They’re not the hardest cyprinid to breed, but they do need specific conditions to trigger spawning, and the eggs and fry require attention. If you’ve bred other egg-scattering cyprinids or tetras, you should be able to manage this species.

Spawning Tank Setup

Set up a separate breeding tank of 10–15 gallons (38–57 liters). Line the bottom with clumps of fine-leaved plants like Java moss or spawning mops — these give the eggs somewhere to settle and provide some protection from the adults. Alternatively, use a mesh or grid on the bottom that allows eggs to fall through while keeping the parents from reaching them. Like most egg scatterers, brilliant rasboras will readily eat their own eggs if they can get to them.

Keep the lighting dim in the breeding tank. A small air-powered sponge filter provides gentle filtration without creating too much current or risking the eggs.

Water Conditions for Breeding

To trigger spawning, aim for soft to moderately soft water with a pH of 6.0–6.5 and hardness around 2–6 dGH. Raise the temperature slightly to 77–79°F (25–26°C). Using RO water mixed with a bit of tap water to hit the target parameters works well. A slight temperature increase combined with a water change can sometimes trigger spawning behavior.

Conditioning & Spawning

Condition breeding pairs or small groups separately for 1–2 weeks before spawning attempts. Feed heavily with high-quality live and frozen foods — daphnia, brine shrimp, and bloodworms are ideal. When females look visibly plump with eggs and males are showing intensified colors, introduce a pair or a small group (2 males to 3 females works well) to the breeding tank in the evening. Spawning typically occurs in the early morning hours.

During spawning, the male will chase and display to the female, and the pair will scatter adhesive eggs among the plants or over the substrate. A healthy female can produce several dozen eggs per spawn.

Egg & Fry Care

Remove the adults immediately after spawning is complete — they will consume every egg they can find. Eggs typically hatch within 24–48 hours depending on temperature. The fry will absorb their yolk sac over the next 2–3 days and become free-swimming shortly after.

Feed free-swimming fry with infusoria or commercial liquid fry food for the first several days. Once they’ve grown a bit, transition to microworms and freshly hatched baby brine shrimp (BBS). Keep the tank clean with small, frequent water changes — fry are sensitive to water quality deterioration. Growth is steady, and young fish should begin showing adult coloration within a few months.

Common Health Issues

Brilliant rasboras are a hardy species overall, but like any aquarium fish, they’re susceptible to a few common diseases. Good husbandry prevents most problems.

Ich (White Spot Disease)

The most common ailment for any tropical fish, and brilliant rasboras are no exception. Ich usually appears after temperature fluctuations, stress from shipping, or introduction to a new tank. Look for small white spots on the body and fins, along with flashing (rubbing against surfaces). Raise the temperature gradually to 82°F (28°C) and treat with a standard ich medication. Brilliant rasboras generally handle treatment well.

Fin Rot

Fin rot is almost always a water quality issue. Ragged, fraying, or discolored fin edges are the telltale signs. Improve water quality with more frequent water changes, and treat with an antibacterial medication if the condition doesn’t improve on its own. Caught early, fin rot is usually easy to reverse.

Columnaris

Columnaris (sometimes mistaken for a fungal infection) appears as white or grayish patches on the body or mouth. It’s bacterial and can spread quickly in stressed or overcrowded tanks. Treat promptly with an appropriate antibiotic, and isolate affected fish if possible.

General Prevention

The best medicine is prevention. Quarantine all new fish for at least two weeks before adding them to your display tank. Maintain stable water parameters, keep up with your water change schedule, and avoid overstocking. Brilliant rasboras are tough fish, but they’re not immune to the basics — good water quality is the foundation of fish health.

Common Mistakes to Avoid

• Keeping too few — Brilliant rasboras are schooling fish. Groups under 6 lead to stressed, skittish fish that spend most of their time hiding. Get at least 6, and aim for 10+ if your tank size allows. A proper school behaves completely differently from a few lonely individuals.
• Too much current — These fish come from slow-moving or still water. A powerful filter output blasting through the tank will stress them out and exhaust them. Diffuse your filter output or use a sponge filter for best results.
• Skipping quarantine — Because they’re often available as wild-caught or farm-raised imports, quarantining new brilliant rasboras for 2 weeks is especially important. It gives you time to spot any diseases before they reach your main tank.
• Pairing with aggressive tank mates — They’re peaceful fish that won’t compete well for food or territory against aggressive species. Stick with other community-friendly fish.
• Ignoring the temperature range — Brilliant rasboras prefer slightly cooler conditions (72–79°F) than many tropical species. Keeping them at the upper end of typical tropical temperatures (82°F+) long-term can shorten their lifespan.

Where to Buy

Brilliant rasboras are occasionally available at well-stocked local fish stores, but they’re not as commonly carried as harlequin rasboras or some of the more popular species. You may need to ask your LFS to special order them, or shop online for a more reliable supply.

For quality stock shipped directly to your door, I recommend checking Flip Aquatics and Dan’s Fish. Both are reputable online sellers that carry healthy, well-acclimated freshwater fish and ship safely. Buying from a dedicated fish seller rather than a big box chain typically means healthier fish with less stress from the supply chain.

Pricing is generally reasonable — expect to pay around $3–5 per fish, with discounts often available when purchasing a full school. Given how hardy and long-lived they are, brilliant rasboras are excellent value.

Frequently Asked Questions

How many brilliant rasboras should I keep together?

A minimum of 6, but 10 or more is ideal. Brilliant rasboras are a true schooling species that feel safest and display the best behavior in larger groups. In small numbers, they become shy and stressed, spending most of their time hiding rather than swimming in the open.

Are brilliant rasboras good for beginners?

Yes, they’re an excellent beginner fish. Their wide tolerance for pH (6.0–8.0) and hardness (2–15 dGH) means they’ll adapt to most tap water without the need for special adjustments. They’re hardy, peaceful, easy to feed, and forgiving of the minor mistakes new fishkeepers often make. Just make sure your tank is fully cycled before adding them.

Can brilliant rasboras live with bettas?

In most cases, yes. Brilliant rasboras are peaceful and not known as fin nippers, which makes them a safer choice for a betta community than many tetras or barbs. Use at least a 20-gallon tank with plenty of plants and hiding spots, and always monitor the betta’s temperament — some individual bettas are more aggressive than others regardless of tank mates.

What’s the difference between brilliant rasboras and harlequin rasboras?

They’re completely different species. Harlequin rasboras (Trigonostigma heteromorpha) are deeper-bodied with a distinctive black triangular patch and coppery-orange coloring. Brilliant rasboras (Rasbora borapetensis) are more streamlined with a black lateral stripe and red-orange tail. Harlequins are also in a different genus — they were reclassified out of Rasbora years ago. Both are great community fish and actually make excellent tank mates together.

Do brilliant rasboras need a heater?

In most homes, yes. While they tolerate temperatures as low as 72°F (22°C), which is close to room temperature in some climates, a heater ensures stability and prevents dangerous nighttime temperature drops. A consistent temperature within their preferred range is more important than the exact number.

Why is my brilliant rasbora’s color fading?

Faded color in brilliant rasboras is usually caused by stress, poor water quality, a monotonous diet, or keeping too few together. Check your water parameters, make sure you have a proper school of 6+, and supplement their diet with frozen foods like brine shrimp and daphnia. A darker substrate and some planted cover can also help bring out their best coloring.

How long do brilliant rasboras live?

With proper care, brilliant rasboras typically live 3 to 5 years in a home aquarium. Consistent water quality, a varied diet, and a low-stress environment with enough schooling companions all help them reach the upper end of that range.

How the Brilliant Rasbora Compares to Similar Species

Brilliant Rasbora vs. Scissortail Rasbora

Both are medium-sized rasboras that need schools and swimming room. The Scissortail Rasbora is more active and has the signature forked tail movement, while the Brilliant Rasbora has better body iridescence. Both are peaceful and hardy. The Scissortail Rasbora is more commonly available.

Brilliant Rasbora vs. Phoenix Rasbora

These are completely different fish for completely different setups. The Phoenix Rasbora is a tiny nano species; the Brilliant Rasbora is a mid-sized schooler. They cannot really be compared as alternatives. choose based on your tank size and goals.

Closing Thoughts

The brilliant rasbora is one of those classic community fish that deserves more attention than it gets. It’s hardy, adaptable, peaceful, and genuinely attractive in a planted setup — what more could you ask for? In a hobby that’s increasingly focused on nano fish and rare imports, there’s something refreshing about a species that just works without any drama.

If you’re building a Southeast Asian community tank or just want a reliable schooling fish that won’t give you headaches, the brilliant rasbora belongs on your shortlist. Give them a proper school, decent water quality, and a tank with some plants and open swimming space, and they’ll reward you with years of trouble-free enjoyment.

Looking for more rasbora and danio species to consider? Check out our complete rasboras and danios guide for profiles on dozens of species.

Recommended Video

Check out this video to learn more about rasboras and which species are best for your tank:

References

• Rasbora borapetensis Profile — Seriously Fish
• Rasbora borapetensis (Smith, 1934) — FishBase
• Brilliant Rasbora — Practical Fishkeeping
• Rasbora borapetensis — The Aquarium Wiki

Table of Contents

• Key Takeaways
• Species Overview
• Classification
• Origin & Natural Habitat
• Appearance & Identification
• Average Size & Lifespan
• Care Guide
• Tank Mates
• Food & Diet
• Breeding & Reproduction
• Common Health Issues
• Common Mistakes to Avoid
• Where to Buy
• Frequently Asked Questions
• Closing Thoughts
• Recommended Video
• References
• What Most Care Guides Get Wrong
• Is the Dwarf Rasbora Right for You?
• Species Comparison

If you’ve caught the nano fish bug, the dwarf rasbora is one of the tiniest and most beautiful freshwater fish you can keep. At barely an inch long, Boraras maculatus packs a surprising amount of color into an incredibly small package, a translucent ruby-red body accented with bold dark spots that make it look like a living gemstone under the right lighting.

This little fish holds some serious bragging rights in the taxonomy world, too. Boraras maculatus is the type species for the entire Boraras genus, the fish that the genus was literally built around. The genus name “Boraras” is actually an anagram of “Rasbora,” and that’s a deliberate nod to how these miniature fish were split off from the much larger Rasbora genus. While true rasboras can reach several inches, every species in Boraras stays well under an inch. They’re a completely different ballgame.

Native to the blackwater peat swamps of the Malay Peninsula, Sumatra, and Singapore, the dwarf rasbora thrives in soft, acidic water that many other fish would struggle in. If you’ve got a planted nano tank with gentle filtration and soft water, this might be the perfect centerpiece fish for it. In my 25+ years in the hobby, I’ve always appreciated how these micro-sized fish can turn a simple 5-gallon planted tank into something genuinely captivating.

What Most Care Guides Get Wrong About Dwarf Rasbora

The most common mistake with Dwarf Rasboras is keeping them in groups that are too small. These fish genuinely need eight to twelve to show natural schooling behavior. In my experience working with rasboras at the stores I managed, small groups of three or four spend all their time hiding.

Key Takeaways

• One of the smallest aquarium fish available: maxes out at just 1 inch (2.5 cm), making it a true nano species ideal for tanks as small as 5 gallons
• Requires soft, acidic water with a pH of 4.0 to 7.0 and hardness of 1 to 5 dGH, this is not a fish for hard, alkaline tap water
• The type species of the Boraras genus, which was split from Rasbora specifically for these miniature fish (the name “Boraras” is an anagram of “Rasbora”)
• Peaceful schooling fish that should be kept in groups of at least 8 to 10 for best color and behavior
• Stunning ruby-red coloration with distinctive dark spots that intensify in soft, tannin-stained water with subdued lighting
• Egg scatterer that can breed in well-maintained planted nano tanks, though raising fry requires dedication and very small first foods

Species Overview

Field	Details
Scientific Name	Boraras maculatus (Duncker, 1904)
Common Names	Dwarf Rasbora, Spotted Rasbora, Pygmy Rasbora
Family	Danionidae
Origin	Southeast Asia (Malay Peninsula, Sumatra, Singapore)
Care Level	Easy to Moderate
Temperament	Peaceful
Diet	Omnivore (micropredator)
Tank Level	Middle
Maximum Size	1 inch (2.5 cm)
Minimum Tank Size	5 gallons (19 liters)
Temperature	73 to 82°F (23 to 28°C)
pH	4.0 to 7.0
Hardness	1 to 5 dGH
Lifespan	3 to 5 years
Breeding	Egg scatterer
Breeding Difficulty	Moderate
Compatibility	Nano community
OK for Planted Tanks?	Yes, ideal choice

Classification

Taxonomic Level	Classification
Order	Cypriniformes
Family	Danionidae (formerly placed in Cyprinidae)
Subfamily	Rasborinae
Genus	Boraras
Species	B. maculatus (Duncker, 1904)

The dwarf rasbora was originally described by Georg Duncker in 1904 as Rasbora maculata. It was later moved into the genus Boraras when Maurice Kottelat established that genus in 1993 to accommodate a group of miniature species that were clearly distinct from the larger true rasboras. Boraras maculatus serves as the type species for the genus, meaning it’s the species that defines what a Boraras is.

The genus name Boraras is an anagram of Rasbora, which is a clever bit of taxonomic wordplay. It reflects the close relationship between the two genera while signaling that Boraras species are fundamentally different, all of them are miniature fish that stay well under 1 inch (2.5 cm), while true Rasbora species can reach several inches. Currently, the genus Boraras contains six recognized species, including popular nano aquarium fish like the chili rasbora (B. brigittae), phoenix rasbora (B. merah), and the least rasbora (B. urophthalmoides).

Like most rasboras, this species was historically classified under the family Cyprinidae. Molecular phylogenetic studies led to the reclassification of many small cyprinids into the family Danionidae, which is now the accepted placement. You may still see Cyprinidae listed on older reference material, but Danionidae is correct.

Origin & Natural Habitat

The dwarf rasbora is native to Southeast Asia, specifically the southern Malay Peninsula (including parts of Malaysia and Singapore) and the island of Sumatra in Indonesia. It has one of the more restricted natural ranges among commonly kept aquarium fish, though it can be locally abundant within that range.

In the wild, B. maculatus is found in peat swamp forests, blackwater streams, and heavily shaded pools associated with ancient tropical peatlands. These are extraordinary environments, the water is often stained a deep tea-brown or almost black by humic acids and tannins leaching from thick layers of decomposing organic matter. The pH in these habitats can drop as low as 3.0 to 4.0, and the water is extremely soft with almost no measurable mineral content. Dissolved oxygen levels can be low, and the substrate is typically a deep bed of waterlogged leaves and woody debris.

Light penetration is minimal due to the dense forest canopy overhead and the deeply stained water. The fish share these habitats with other acid-loving species like chocolate gouramis, licorice gouramis, and various other Boraras species. Understanding just how extreme these blackwater conditions are helps explain why the dwarf rasbora does so much better in soft, acidic aquarium water. These fish evolved in water that most fishkeepers would consider impossibly acidic.

It’s worth noting that many of these peat swamp habitats are under serious threat from deforestation, agricultural conversion (particularly oil palm plantations), and peat drainage. Conservation of these ecosystems matters not just for the dwarf rasbora but for the dozens of unique fish species that call them home.

Appearance & Identification

The dwarf rasbora is a tiny, slender-bodied fish with a translucent to semi-translucent base color that ranges from pinkish-red to a deep ruby-red depending on the fish’s condition, water chemistry, and diet. When kept in optimal soft, acidic water with tannins, the red coloration becomes rich and intense. In harder or more alkaline water, the color fades to a washed-out pinkish-orange.

The most distinguishing feature of B. maculatus is its pattern of dark spots. There are typically three prominent dark markings: one near the base of the anal fin, one on the caudal peduncle (the narrow area just before the tail), and one larger spot on the mid-body near the base of the dorsal fin. These dark blotches are bordered or highlighted by areas of more intense red or orange pigment, creating a striking contrast against the translucent body.

The fins are mostly transparent to slightly reddish, and the eye is relatively large for the body size, with a dark pupil and a thin golden or reddish iris. The overall body shape is torpedo-like but very petite, these are genuinely tiny fish, and seeing them in person for the first time, most people are surprised by just how small they actually are.

Telling Boraras Species Apart

With six species in the genus, Boraras can be confusing, especially since several look similar at first glance and mislabeling in the trade is common. Here’s a quick breakdown of the most commonly available species:

• Dwarf Rasbora (B. maculatus): Ruby-red body with distinct dark spots (typically three visible). This is the type species for the genus and one of the most widely available.
• Chili Rasbora (B. brigittae): Deeper, more intense red coloration with a prominent dark lateral stripe running along the body rather than isolated spots. Generally considered the most vibrantly colored Boraras species.
• Phoenix Rasbora (B. merah): Similar to the chili rasbora but with a shorter, less defined lateral stripe and more prominent dark spots. The red coloration tends to be slightly more orange-toned.
• Least Rasbora (B. urophthalmoides): Has a thin dark lateral stripe with a distinct dark spot at the base of the tail. Body color is more golden-orange than ruby-red. Slightly more elongated body shape.
• Exclamation Point Rasbora (B. urophthalmoides): Sometimes sold under this common name, same species as the least rasbora. The name comes from the combination of the lateral stripe and tail spot resembling an exclamation mark.

The key to telling B. maculatus apart from its relatives: look for distinct, rounded dark spots rather than a continuous lateral stripe. If you see a solid dark line running along the body, you’re more likely looking at a chili rasbora or phoenix rasbora.

Male vs. Female

Sexing dwarf rasboras takes patience, but there are some differences in mature fish:

• Males tend to be slightly slimmer and display more intense red coloration, especially when displaying to other males or courting females. Their dark spots may also appear more sharply defined.
• Females are slightly rounder and deeper-bodied, particularly when carrying eggs. When viewed from above, gravid females have a noticeably plumper profile compared to the more streamlined males.

These differences are subtle at best and nearly impossible to see in juvenile fish. Having a group of 8 or more adults makes the distinctions easier to spot as the males and females naturally sort themselves out during social interactions.

Average Size & Lifespan

The dwarf rasbora is one of the smallest freshwater fish available in the aquarium hobby. Maximum size is right around 1 inch (2.5 cm) in total length, and most specimens in home aquariums will be closer to 0.6 to 0.8 inches (1.5 to 2 cm). They really are remarkably tiny, if you’ve only kept standard community fish like tetras or barbs, seeing a dwarf rasbora for the first time can be a bit of a shock.

Despite their diminutive size, dwarf rasboras have a respectable lifespan of 3 to 5 years with proper care. Stable water conditions, appropriate water chemistry (soft and acidic), a varied diet of small foods, and a stress-free environment are the keys to longevity. Poor water quality and improper parameters will shorten their lifespan significantly, these small-bodied fish have very little margin for error when conditions deteriorate.

Care Guide

Dwarf rasboras are not particularly demanding fish, but they do have some strong preferences that you’ll need to accommodate. The biggest thing to understand is that these are softwater, acidic-water fish to their core. They come from some of the most acidic natural habitats of any commonly kept aquarium fish, and while they don’t need pH 4.0 water in captivity, they absolutely need soft, acidic conditions to thrive and show good color.

Tank Size

A 5-gallon tank is the minimum for a small group of dwarf rasboras, and honestly, a 5-gallon planted nano tank with 8 to 10 of these fish can be one of the most beautiful small aquariums you’ll ever set up. A 10-gallon gives you more room to work with, you can keep a larger group of 12 to 15 and have space for a few tank mates like dwarf shrimp or pygmy corydoras.

These are mid-level swimmers that don’t need a lot of vertical space. Longer, shallower tanks are preferable to tall, narrow ones. A 10-gallon standard or a 5-gallon long-style nano tank works beautifully. Whatever size you choose, stability is the key concern. Smaller tanks experience faster parameter swings, which these tiny fish are sensitive to. If you’re new to nano fishkeeping, starting with a 10-gallon gives you a bit more of a buffer.

Water Parameters

Parameter	Recommended Range
Temperature	73 to 82°F (23 to 28°C)
pH	4.0 to 7.0 (prefers 5.0 to 6.5)
General Hardness (GH)	1 to 5 dGH
Carbonate Hardness (KH)	0 to 4 dKH
Ammonia / Nitrite	0 ppm
Nitrate	Below 20 ppm

Here’s where the dwarf rasbora gets a little more specialized than your average community fish. These fish genuinely prefer acidic water, not just slightly acidic, but properly acidic. In the wild they live in water with pH values as low as 3.0 to 4.0. In the aquarium, they’ll do well in a pH range of about 5.0 to 6.5, and they can tolerate up to neutral (7.0) without issues. Going above 7.0 is where you’ll start to see problems, faded color, reduced activity, and increased susceptibility to disease.

Water hardness is just as important as pH. These are soft water fish, period. If your tap water is above 5 dGH, you’ll almost certainly need to use RO/DI water remineralized with a product like Seachem Equilibrium, or blend RO water with your tap water until you hit the right range. Running them in hard, alkaline water is a recipe for pale, stressed fish that won’t live anywhere near their potential lifespan.

Indian almond leaves, alder cones, and driftwood all release tannins that naturally lower pH and add the humic substances these fish are adapted to. A blackwater-style setup isn’t just aesthetically appealing for this species, it’s genuinely beneficial for their health and coloration.

Filtration & Water Flow

These fish come from nearly stagnant water, so strong filtration and high flow are not what they want. A sponge filter is the ideal choice for a dwarf rasbora tank. It provides gentle biological filtration, creates minimal water movement, and won’t suck up tiny fish or fry. For slightly larger setups, a small hang-on-back filter with the outflow baffled (a piece of filter sponge over the output works great) is also fine.

Avoid canister filters or powerheads that create strong currents in a nano tank with these fish. They’ll spend all their energy fighting the current instead of displaying their natural, relaxed schooling behavior. If you can see the fish being pushed around by the water flow, it’s too strong.

Lighting

Dwarf rasboras come from dimly lit, heavily shaded blackwater environments, and they look and behave best under moderate to low lighting. Bright lights will make them skittish, washed out, and prone to hiding. If you’re running a planted tank that needs higher light for your plants, add plenty of floating plants, water sprite, frogbit, red root floaters, or salvinia, to create shaded areas. The fish will naturally gravitate toward these darker zones, and their ruby-red color will look far more vivid in softer light.

Plants & Decorations

A well-planted tank is strongly recommended for dwarf rasboras. Dense planting provides security, creates visual barriers that reduce stress, and mimics their natural environment. Great plant choices include:

• Cryptocoryne species: Thrive in soft, acidic water just like these fish. Perfect for mid and foreground planting.
• Java fern and Anubias: Hardy, low-light plants that attach to driftwood and provide broad leaves and hiding spots
• Java moss and other mosses: Excellent for providing cover for fry and creating a natural-looking carpet or covering on hardscape
• Floating plants: Water sprite, frogbit, salvinia, or red root floaters to diffuse lighting and add root structure
• Bucephalandra: Another slow-growing epiphyte that does well in soft water and low to moderate light

Driftwood is almost a must-have. It releases tannins that these fish benefit from and creates a natural-looking blackwater aesthetic. Scatter some dried Indian almond leaves or oak leaves on the substrate for an authentic peat swamp look. The leaves will slowly decompose, release tannins, and harbor microorganisms that the fish will graze on between feedings. Leave an open swimming area in the front or center of the tank so you can actually watch the school move together.

Substrate

A dark substrate is the way to go. Dark sand, fine dark gravel, or an active aqua soil all work well. Active substrates designed for planted tanks are particularly good because many of them buffer the water toward an acidic pH, which is exactly what these fish need. ADA Amazonia and similar products are excellent choices if you’re setting up a dedicated dwarf rasbora nano tank.

Avoid bright white or light-colored substrates. They make the fish feel exposed, wash out their coloration, and don’t reflect the dark, leaf-covered bottoms these fish are accustomed to in the wild.

Tank Mates

Tank mate selection for dwarf rasboras requires some careful thought because of their extremely small size. At under an inch, these fish can fit in the mouth of a surprisingly wide range of other species. You need to think nano-scale when choosing companions, only the smallest, most peaceful fish and invertebrates belong in the same tank.

Best Tank Mates

• Other Boraras species: Chili rasboras, phoenix rasboras, least rasboras. They share identical care requirements and look fantastic together in a mixed Boraras display.
• Pygmy corydoras (Corydoras pygmaeus): Tiny bottom dwellers that stay small enough to be safe companions
• Habrosus corydoras (Corydoras habrosus): Another miniature cory that’s a perfect nano tank mate
• Ember tetras: Small, peaceful, and also do well in soft, acidic water
• Sparkling gouramis: Calm, tiny gouramis that share a preference for blackwater conditions
• Chocolate gouramis: Share the exact same blackwater habitat in the wild (for experienced keepers)
• Dwarf shrimp: Cherry shrimp, crystal red shrimp, and other neocaridina or caridina species. Adult shrimp are safe; baby shrimp may occasionally be eaten.
• Small snails: Nerite snails, ramshorn snails, Malaysian trumpet snails
• Otocinclus catfish: Gentle algae eaters, though they prefer slightly different water chemistry

Tank Mates to Avoid

• Any fish large enough to eat them: This rules out most standard community fish. Even a peaceful 2-inch tetra could potentially view a dwarf rasbora as food.
• Bettas: Even in a nano tank, most bettas will harass or eat fish this small
• Dwarf cichlids: Apistogramma and rams are too large and territorial for a nano tank with dwarf rasboras
• Tiger barbs and other nippy species: Way too aggressive and active for these tiny, delicate fish
• Large shrimp species: Amano shrimp are generally fine, but be cautious with larger species like bamboo shrimp in very small tanks
• Any aggressive or highly active species: Fast-moving fish will outcompete them for food and stress them out

Honestly, a species-only tank with just a group of 10 to 15 dwarf rasboras and some dwarf shrimp is one of the most rewarding nano setups you can build. Don’t feel like you need to fill the tank with other species. Sometimes less is more.

Food & Diet

Dwarf rasboras are omnivorous micropredators with very small mouths. In the wild, they feed on tiny insects, worms, zooplankton, and other microscopic organisms found among leaf litter and decomposing plant matter. In the aquarium, food size is the biggest consideration, these fish physically cannot eat standard-sized flakes or pellets.

A good feeding plan includes:

• Micro pellets or finely crushed flakes: Look for high-quality products specifically designed for nano fish. The food particles need to be small enough for a sub-1-inch mouth.
• Frozen foods: Baby brine shrimp, daphnia, cyclops, and micro bloodworms are all excellent. These small frozen foods are some of the best everyday options for Boraras species.
• Live foods: Baby brine shrimp, microworms, vinegar eels, daphnia, and grindal worms. Live foods bring out the best feeding response and are essential for conditioning breeders.
• Freeze-dried foods: Crushed freeze-dried tubifex or daphnia as an occasional supplement, pre-soaked to prevent digestive issues.

Feed small amounts once or twice daily. These are tiny fish with tiny stomachs, and overfeeding is one of the fastest ways to crash water quality in a nano tank. Offer only what the group can consume in about 60 seconds. If food is hitting the substrate uneaten, you’re feeding too much. In a well-planted tank with leaf litter, the fish will also graze on biofilm and microorganisms between feedings, which helps supplement their diet naturally.

Is the Dwarf Rasbora Right for You?

Before you add a Dwarf Rasbora to your tank, here is an honest assessment of what you’re signing up for. I’d rather you know exactly what to expect now than find out the hard way after you’ve already bought one.

• Experience level: Dwarf Rasboras are best suited for intermediate to advanced keepers. They have specific requirements that can overwhelm beginners.
• Tank size commitment: You’ll need at least 5 gallons, though bigger is always better. Make sure you have room for the tank before buying.
• Tank mate planning: Dwarf Rasboras can be territorial, so plan your community carefully. Not every fish will work as a tank mate.
• Maintenance demands: Expect regular water testing and consistent water changes. Dwarf Rasboras are sensitive to parameter fluctuations.
• Budget reality: Keeping Dwarf Rasboras costs more than typical setups. Budget for ongoing costs, not just the initial purchase.
• Time investment: Beyond daily feeding and weekly maintenance, regular observation is the best way to catch health issues early.
• Long-term commitment: With proper care, Dwarf Rasboras can live up to 5 years. Make sure you’re ready for years of consistent care.

Breeding & Reproduction

Breeding dwarf rasboras is achievable, though it requires some patience and attention to detail. These are egg scatterers that don’t provide any parental care, so the challenge is mainly about creating the right conditions and protecting the eggs and fry from being eaten.

Breeding Difficulty

Moderate. In well-maintained planted nano tanks with soft, acidic water, dwarf rasboras may actually spawn on their own without any intervention. The challenge isn’t triggering spawning, it’s getting the fry to survive. In a community setting, eggs and fry are almost always consumed by other fish (including the parents). Raising fry requires either a dedicated breeding setup or an extremely densely planted tank where some fry can hide.

Spawning Tank Setup

If you want to breed dwarf rasboras intentionally, set up a small breeding tank of 2.5 to 5 gallons with:

• Very dim lighting or a heavily shaded environment
• An air-driven sponge filter on the lowest possible setting
• Clumps of fine-leaved plants like java moss, Taxiphyllum, or spawning mops to catch the scattered eggs
• A bare bottom or a thin layer of dark substrate
• A cover on the tank, keep the environment calm and undisturbed

Water Conditions for Breeding

Soft, acidic water is essential for successful breeding. Target:

• Temperature: 78 to 82°F (26 to 28°C), slightly warmer than normal maintenance temperature
• pH: 5.0 to 6.0
• Hardness: 1 to 3 dGH (very soft)

RO water with minimal remineralization is ideal. Adding Indian almond leaves or peat filtration helps achieve the low pH and provides the tannin-rich water these fish naturally breed in.

Conditioning & Spawning

Condition a small group (ideally 3 to 4 females and 2 to 3 males) with plenty of live and frozen foods for about two weeks prior to breeding attempts. Baby brine shrimp, daphnia, and microworms are excellent conditioning foods. Well-conditioned females will become visibly rounder as they fill with eggs.

Introduce the group to the breeding tank in the evening. Spawning typically occurs in the early morning hours. The male courts the female with subtle displays, and the pair scatters small, adhesive eggs among fine-leaved plants or moss. A single spawning event may produce 30 to 50 eggs, though clutch sizes vary. The eggs are very small and can be difficult to spot.

Egg & Fry Care

Remove the adults after spawning, as they will eat the eggs without hesitation. The eggs hatch in approximately 24 to 48 hours depending on temperature. The fry are absolutely minuscule, among the smallest you’ll encounter in freshwater fishkeeping.

Newly hatched fry will absorb their yolk sac over the first 24 to 48 hours. Once they become free-swimming, they need extremely small first foods. Infusoria (paramecium cultures) or commercially available liquid fry foods are necessary for the first 7 to 10 days. After that, you can transition to freshly hatched baby brine shrimp and microworms. Keep the water extremely clean with very small, careful water changes. Growth is slow, and it takes several weeks for the fry to develop recognizable coloration. Patience is essential.

Common Health Issues

Dwarf rasboras are reasonably hardy when kept in appropriate conditions, but their small body size means they have less reserve to fight off illness. Prevention through proper water quality and stable parameters is far more effective than treatment with this species. Here are the most common issues:

Ich (White Spot Disease)

The most common disease in freshwater aquariums, and dwarf rasboras are susceptible when stressed by temperature fluctuations, poor water quality, or new introductions. Look for small white dots resembling grains of salt on the body and fins. Treat by gradually raising the temperature to 82 to 84°F (28 to 29°C) and using a half dose of ich medication, these small fish can be sensitive to full-strength chemical treatments. Always follow the medication instructions carefully and remove any activated carbon from the filter during treatment.

Fin Rot

Deteriorating, ragged fins indicate a bacterial infection, usually brought on by poor water conditions. In a nano tank, water quality can decline rapidly if maintenance is skipped. Improving water quality through frequent small water changes is often enough to resolve mild cases. Severe fin rot may require an antibacterial treatment.

Bacterial Infections

Columnaris and other bacterial infections can appear as white or grayish patches on the body, mouth, or fins. These are typically triggered by stress from improper water parameters, particularly keeping dwarf rasboras in water that’s too hard or too alkaline. Getting the water chemistry right is the best prevention. Treatment with antibacterial medications may be necessary for active infections, but use reduced doses given the small body size of these fish.

Velvet Disease

Velvet (caused by Piscinoodinium) appears as a fine gold or rust-colored dust on the skin, often visible when you shine a flashlight at an angle across the fish. It’s more common in warm, soft water, exactly the conditions dwarf rasboras prefer. Affected fish may clamp their fins and scratch against surfaces. Treatment typically involves raising the temperature slightly, dimming the lights, and using a copper-based medication at a reduced dose.

The single best preventive measure for all of these issues is maintaining clean, stable water conditions. In nano tanks, that means weekly water changes of 20 to 30%, testing your parameters regularly, not overstocking, and quarantining all new fish before adding them to an established tank.

Common Mistakes to Avoid

• Keeping them in hard, alkaline water. This is the number one mistake. Dwarf rasboras need soft, acidic water to thrive. If your tap water is pH 7.5+ or above 8 dGH, you need to use RO water. Running them in hard water leads to faded color, chronic stress, and shortened lifespans.
• Groups that are too small. A pair or trio of dwarf rasboras will hide, stress, and fade. You need a minimum of 8, and 10 to 15 is better. In a proper-sized school, they’re confident, active, and brilliantly colored. In a group of 3, they’re a ghost of what they should be.
• Feeding food that’s too large. Standard-sized flakes and pellets are literally too big for these fish to eat. You need micro pellets, crushed flakes, or frozen foods sized for nano fish. If the food particles are bigger than their mouths, they’ll go hungry.
• Overstocking a nano tank. Just because they’re small doesn’t mean you can cram 20 of them into a 3-gallon tank. Respect the minimum tank sizes and bioload limits. A 5-gallon is the minimum for 8 to 10 fish.
• Too much light, not enough cover. Bright, unshaded lighting makes these fish pale and skittish. Add floating plants and plant densely to create the shaded, secure environment they need.
• Housing them with inappropriate tank mates. Any fish over about 1.5 inches is potentially a predator of dwarf rasboras. Think nano-scale when choosing companions. A “peaceful” 3-inch fish is still a death sentence for a 0.7-inch rasbora.
• Neglecting water changes in a nano tank. Small tanks accumulate waste quickly. Skipping water changes for even a week or two in a 5-gallon tank can lead to dangerous parameter spikes. Consistency is everything with nano fishkeeping.

Where to Buy

Dwarf rasboras are moderately available in the hobby. You’re unlikely to find them at chain pet stores, but specialty aquarium shops and online retailers frequently carry them, especially shops that cater to the planted tank and nano fish crowd. Prices are typically in the $3 to $5 per fish range, and buying in bulk (10 or more) often gets you a better deal.

For healthy, well-conditioned fish that have been properly quarantined before shipping, I’d recommend checking Flip Aquatics or Dan’s Fish. Both are reputable online retailers that specialize in quality freshwater fish and ship in excellent condition. Buying online is often the best option for nano species like this, since local fish stores may not stock them regularly and you want to get a proper-sized group all at once.

When buying dwarf rasboras, look for fish that are active, alert, and showing decent color. Avoid any that appear lethargic, have clamped fins, or show visible spots or patches. And double-check the species, Boraras species are frequently mislabeled in the trade, so confirm you’re looking at B. maculatus (dark spots, not a lateral stripe) before you buy.

Frequently Asked Questions

What’s the difference between the dwarf rasbora and the chili rasbora?

Both are Boraras species and share very similar care requirements, but they look quite different once you know what to look for. The dwarf rasbora (B. maculatus) has distinct, rounded dark spots on a ruby-red body. The chili rasbora (B. brigittae) has a continuous dark lateral stripe running along its body with a vivid red stripe above it. The chili rasbora is widely recognized as the more intensely colored of the two, with a deeper, more saturated red. Both are excellent nano tank fish, and they can actually be kept together in the same aquarium since they share identical water parameter requirements.

How many dwarf rasboras should I keep?

A minimum of 8, with 10 to 15 being ideal. These are schooling fish that need a group to feel secure and display natural behavior. In a proper-sized school, they’ll stay out in the open, show their best coloration, and exhibit fascinating social interactions between males. In groups of fewer than 6, they’ll hide, stress, and look pale. More is genuinely better with this species.

Can dwarf rasboras live in a 3-gallon tank?

I wouldn’t recommend it. While they’re small enough to physically fit, a 3-gallon tank doesn’t provide enough water volume for stable parameters, and these fish need a group of at least 8 to thrive. A 5-gallon is the true minimum, and a 10-gallon is a much safer and more forgiving starting point. The smaller the tank, the faster water quality deteriorates, and nano fish like dwarf rasboras are sensitive to those swings.

Do dwarf rasboras need a heater?

In most homes, yes. Their preferred temperature range is 73 to 82°F (23 to 28°C). Unless your room temperature consistently stays above 73°F year-round, you’ll need a small heater to keep things stable. In a nano tank, a low-wattage preset heater (25 watts for a 5-gallon, 50 watts for a 10-gallon) is usually sufficient. Temperature stability matters more than hitting an exact number, avoid swings of more than 2 to 3 degrees in a day.

Are dwarf rasboras good with shrimp?

Adult cherry shrimp, crystal red shrimp, and other dwarf shrimp are generally safe with dwarf rasboras. However, shrimplets (baby shrimp) may be eaten since they’re small enough to fit in the rasboras’ mouths. If you’re actively breeding shrimp, provide plenty of dense moss and plant cover for the babies to hide in. This isn’t a species that hunts shrimp, but opportunistic snacking on newborn shrimplets is always a possibility with any fish, no matter how small.

Why are my dwarf rasboras pale?

Pale coloration in dwarf rasboras is almost always caused by one or more of these factors: water that’s too hard or alkaline (check your pH and GH first), too-bright lighting without enough shade, a group that’s too small, stress from aggressive or overly active tank mates, or a bland diet lacking frozen and live foods. Getting the water soft and acidic, adding floating plants for shade, keeping a group of 8 or more, and feeding a varied diet with frozen baby brine shrimp and daphnia will usually resolve the issue within a couple of weeks.

How the Dwarf Rasbora Compares to Similar Species

If you’re considering a Dwarf Rasbora, you’ve probably also looked at the Chili Rasbora. Both fill similar roles, but the differences matter when planning your tank. The Dwarf Rasbora has its own distinct personality and care needs. In my experience, the choice often comes down to the specific community you’re building and whether your water parameters favor one over the other.

The Strawberry Rasbora is worth considering as well. While the Dwarf Rasbora and the Strawberry Rasbora share some overlap in care, they bring different energy to a tank. If you have the space, keeping both in separate setups gives you a great chance to compare their behavior firsthand.

Closing Thoughts

The dwarf rasbora is one of those fish that really shows you what nano fishkeeping is all about. In a properly set up blackwater nano tank, soft acidic water, dense planting, tannin-stained water, dim lighting, a school of these tiny ruby-red fish is genuinely breathtaking. They’re living proof that you don’t need a massive aquarium or big, flashy fish to create something beautiful.

As the type species for the Boraras genus, B. maculatus has a special place in the nano fishkeeping world. It’s the fish that started it all for this group of miniature rasboras that have become some of the most sought-after species among planted tank enthusiasts. Keep them in a proper school, give them the soft, acidic water they crave, feed small foods regularly, and they’ll reward you with years of subtle, jewel-like beauty. If you’re looking to set up a nano tank that packs real visual impact into a small footprint, the dwarf rasbora belongs at the top of that list. Get the water soft, the group to 10 or more, and the substrate dark. A blackwater nano with these tiny red dots moving through it is the setup that makes other nano keepers stop and ask what that fish is.

Recommended Video

Check out our rasbora video for more on these amazing nano fish, including the dwarf rasbora:

References

• Boraras maculatus (Duncker, 1904) – FishBase
• Boraras maculatus Profile – Seriously Fish
• Dwarf Rasbora Care Guide – Practical Fishkeeping
• Kottelat, M. (1993). “Diagnoses of two new genera and three new species of small fishes from Thailand.”, Ichthyological Exploration of Freshwaters, 4(4): 313-320.

Table of Contents

• Key Takeaways
• Species Overview
• Classification
• Origin & Natural Habitat
• Appearance & Identification
• Average Size & Lifespan
• Care Guide
• Tank Mates
• Food & Diet
• Breeding & Reproduction
• Common Health Issues
• Common Mistakes to Avoid
• Where to Buy
• Frequently Asked Questions
• Closing Thoughts
• Recommended Video
• References
• What Most Care Guides Get Wrong
• Is the Copper Rasbora Right for You?
• Species Comparison

If you’ve ever looked at a school of rasboras in a dimly lit planted tank and noticed one species that seemed to glow from within, there’s a good chance you were looking at copper rasboras. Trigonostigma hengeli is the smallest and arguably the most striking of the three closely related Trigonostigma species, and that bright copper-orange blaze above its dark body marking is unlike anything else in the nano fish world.

Also known as the hengeli rasbora or glowing rasbora, this little fish from Borneo and Sumatra doesn’t get nearly the attention it deserves. The harlequin rasbora has the name recognition. The lambchop rasbora has been gaining fans. But the copper rasbora? It quietly sits there being the most luminous of the bunch, waiting for hobbyists to discover it. In my 25+ years in the hobby, I’ve seen this species go from almost unknown to a real favorite among planted tank enthusiasts, and for good reason. Once you see that neon copper glow in person, it’s hard to go back to anything else.

What Most Care Guides Get Wrong About Copper Rasbora

The most common mistake with Copper Rasboras is keeping them in groups that are too small. These fish genuinely need eight to twelve to show natural schooling behavior. In my experience working with rasboras at the stores I managed, small groups of three or four spend all their time hiding.

Key Takeaways

• Smallest of the Trigonostigma trio at just 1.25 inches (3 cm) max, a true nano fish with an oversized visual impact thanks to its signature copper-orange glow
• Soft, acidic water brings out the best color: they prefer pH 5.0 to 7.0 and 2 to 10 dGH, and their glow intensifies dramatically in tannin-stained blackwater setups
• Peaceful schooling fish that should be kept in groups of 8 or more for the best behavior and color expression
• Easy to confuse with harlequin and lambchop rasboras: the copper rasbora has the thinnest dark marking of the three, reduced to a narrow line, with a vivid copper-orange glow directly above it
• Minimum 10-gallon tank for a school of 6 to 8, though a 15 to 20-gallon planted setup really lets them shine
• Egg scatterer that deposits on leaf undersides: breeding is moderately challenging and requires very soft, acidic water

Species Overview

Field	Details
Scientific Name	Trigonostigma hengeli (Meinken, 1956)
Common Names	Copper Rasbora, Hengeli Rasbora, Glowing Rasbora
Family	Danionidae
Origin	Southeast Asia (Borneo, Sumatra)
Care Level	Easy
Temperament	Peaceful
Diet	Omnivore
Tank Level	Middle
Maximum Size	1.25 inches (3 cm)
Minimum Tank Size	10 gallons (38 liters)
Temperature	73 to 82°F (23 to 28°C)
pH	5.0 to 7.0
Hardness	2 to 10 dGH
Lifespan	3 to 5 years
Breeding	Egg scatterer (deposits on leaf undersides)
Breeding Difficulty	Moderate
Compatibility	Community (nano)
OK for Planted Tanks?	Yes, excellent choice

Classification

Taxonomic Level	Classification
Order	Cypriniformes
Family	Danionidae (formerly placed in Cyprinidae)
Subfamily	Rasborinae
Genus	Trigonostigma
Species	T. hengeli (Meinken, 1956)

The copper rasbora was described by Hermann Meinken in 1956. It belongs to the genus Trigonostigma, which was separated from the much larger Rasbora genus and currently contains three widely recognized species: the harlequin rasbora (T. heteromorpha), the lambchop rasbora (T. espei), and the copper rasbora (T. hengeli). A fourth species, T. somphongsi, is also recognized but is critically endangered and virtually absent from the aquarium trade.

Like other rasboras, this species was historically classified under the family Cyprinidae. Molecular phylogenetic studies led to the reclassification of many rasbora species into the family Danionidae, which is now the accepted placement. You may still see Cyprinidae referenced in older aquarium books and websites, but Danionidae is the current correct family.

Origin & Natural Habitat

The copper rasbora is native to the islands of Borneo and Sumatra in Southeast Asia, specifically in parts of Indonesia. This is a notably different range from its two close relatives, the harlequin rasbora is found across the Malay Peninsula and Sumatra, while the lambchop rasbora comes from Thailand and Cambodia. The copper rasbora’s island-based distribution makes it the most geographically restricted of the three common Trigonostigma species.

In the wild, T. hengeli inhabits slow-moving forest streams, peat swamps, and blackwater environments shaded by thick tropical forest canopy. These habitats are characterized by extremely soft, acidic water, often with a pH below 5.0, that is heavily stained by tannins from decomposing leaves, wood, and other organic material. The substrate is typically composed of deep leaf litter over soft mud or peat, and light levels are very low due to the combination of dense overhead canopy and dark water.

These are warm, still waters with very little current. The fish share their habitat with other small cyprinids, gouramis, and various invertebrates. Understanding these natural conditions is critical for keeping copper rasboras at their best. When you replicate the dim lighting, soft acidic water, and tannin-stained environment of their home waters, that iconic copper glow reaches an intensity you simply won’t see in a bright, hard-water tank.

Appearance & Identification

The copper rasbora has a small, slender, laterally compressed body with a semi-translucent quality that lets light pass through in a way that adds to its visual appeal. The base body color is a warm silvery-tan to pinkish-orange, generally more translucent and less deeply pigmented than either the harlequin or lambchop rasbora. The belly is pale silver, and the back takes on a slightly olive or golden tone.

The feature that sets this species apart from every other nano fish in the hobby is the combination of its dark marking and the vivid copper-orange glow above it. The dark marking itself is noticeably thinner than what you’ll see on its relatives, more of a narrow dark stripe or sliver running along the rear half of the body, rather than a broad triangle or wedge. And directly above that thin dark line sits a concentrated band of bright copper, orange, or even neon-gold color that seems to glow under the right lighting conditions. This luminous stripe is the hallmark of T. hengeli and the main reason it’s called the “copper” or “glowing” rasbora.

The fins are transparent to faintly yellowish, and the eye has a dark pupil with a golden iris. In well-kept specimens under appropriate conditions, the copper glow can be almost startlingly bright, a neon shimmer that looks like the fish is lit from within.

The Trigonostigma Trio: Hengeli vs. Heteromorpha vs. Espei

These three species are the most commonly confused fish in the rasbora world, and mislabeling at fish stores is extremely common. All three share a similar body plan with a dark marking on the rear half of the body, but each species has a distinctly different version of that marking. Here’s how to tell them apart:

• Harlequin Rasbora (T. heteromorpha): The largest of the three, reaching up to 2 inches (5 cm). Has the broadest, most triangular dark marking that covers a large portion of the rear body. The triangle is wide and prominent with a fairly straight leading edge. The body is deeper and stockier than the other two species. This is the most widely available and best-known species in the genus.
• Lambchop/Espei Rasbora (T. espei): Mid-sized at about 1.5 inches (3.5 cm). The dark marking is narrower and more elongated than the harlequin’s, shaped like a thin wedge or lamb chop. The body is slimmer and more streamlined, with a warmer copper-orange base color. If the marking looks like a “squeezed” version of the harlequin’s triangle, you’re looking at an espei.
• Copper/Hengeli Rasbora (T. hengeli): The smallest of the three, maxing out at just 1.25 inches (3 cm). Has the thinnest dark marking of the group, reduced to a narrow dark line or sliver rather than any kind of triangle. The defining feature is the bright copper or neon-orange glow directly above that dark line, which is far more vivid and concentrated than anything you’ll see on the other two species. The overall body is more translucent and delicate-looking.

The quick identification guide: broad triangle = harlequin, narrow wedge = lambchop, thin line with a bright copper glow above it = hengeli. If you’re buying these at a local fish store, pay close attention to the shape and width of that dark marking and whether there’s a vivid copper stripe above it. The label in the tank is frequently wrong, especially since all three species sometimes get lumped together as “harlequin rasboras.” Take a close look at the actual fish before you buy.

Male vs. Female

Sexing copper rasboras is tricky, but there are a few subtle differences in mature fish:

• Males tend to be slightly slimmer and more intensely colored, particularly in the copper-orange zone above the dark marking. They may also display more vivid coloration during courtship and when competing with other males in the group.
• Females are typically a bit rounder and deeper-bodied, especially when carrying eggs. Their coloration is usually slightly less intense than males, though both sexes display the characteristic copper glow.

These differences are subtle and are easiest to spot when you have a group of adult fish for side-by-side comparison. Don’t expect to reliably sex juveniles or newly purchased fish, it usually takes a few weeks in good conditions before the differences become apparent.

Average Size & Lifespan

Copper rasboras are the smallest of the three common Trigonostigma species, maxing out at about 1.25 inches (3 cm) in total length. Most specimens you’ll see in home aquariums will be around 0.75 to 1 inch (2 to 2.5 cm). This makes them a true nano fish, small enough to keep in tanks that would be too cramped for larger schooling species.

With proper care, stable water conditions, and a varied diet, copper rasboras typically live 3 to 5 years. Some hobbyists have kept them toward the upper end of that range in well-maintained planted tanks with soft water. As with most small fish, poor water quality, stress from inadequate group sizes, and wide parameter fluctuations will cut that lifespan short.

Care Guide

Copper rasboras are not demanding fish, but they have clear preferences when it comes to water chemistry and environment. They’re forgiving enough for beginners who do their homework, but getting the water parameters right is what separates a tank full of pale, washed-out fish from a school that glows like embers. Get the basics right and these fish practically take care of themselves.

Tank Size

A 10-gallon tank is the minimum for a small group of 6 to 8 copper rasboras. Given their tiny size, they don’t need a massive aquarium, but more space is always better. A 15 to 20-gallon tank gives a larger school of 10 to 15 fish room to display natural schooling behavior, and the extra water volume provides more stability for the soft, acidic conditions they prefer.

These fish occupy the middle portion of the water column, so horizontal swimming space matters more than tank height. Long, shallow tanks are a better fit than tall, narrow ones. A 20-gallon long is an excellent choice if you’re building a community around this species.

Water Parameters

Parameter	Recommended Range
Temperature	73 to 82°F (23 to 28°C)
pH	5.0 to 7.0
General Hardness (GH)	2 to 10 dGH
Carbonate Hardness (KH)	1 to 4 dKH
Ammonia / Nitrite	0 ppm
Nitrate	Below 20 ppm

Soft, acidic water is where copper rasboras come alive. They can tolerate neutral pH, but their signature copper glow intensifies dramatically in water below pH 6.5. These are blackwater fish at heart, and when you provide conditions that reflect that, soft water, low pH, tannins, the difference in coloration is night and day.

If your tap water is hard and alkaline (above pH 7.0 or above 10 dGH), you’ll want to use RO/DI water remineralized with a product like Seachem Equilibrium, or blend RO water with tap water to bring the hardness down. Adding Indian almond leaves, alder cones, or driftwood to the tank releases tannins that naturally lower pH and give the water a warm amber tint. This isn’t just cosmetic, it closely replicates the peat swamp habitats these fish evolved in, and they respond to it with better color and more confident behavior.

Filtration & Water Flow

Copper rasboras come from nearly still water, so strong currents are a no-go. A sponge filter is the ideal filtration option for smaller tanks housing this species, it provides gentle biological filtration with minimal flow and won’t create currents that push these tiny fish around. In larger setups, a hang-on-back or small canister filter with the output baffled or directed at the glass works well. The goal is just enough surface agitation for gas exchange without any noticeable current in the swimming area.

Lighting

Subdued lighting is the way to go with copper rasboras. In their natural habitat, thick forest canopy and dark tannin-stained water mean very little light reaches the fish. In an aquarium, dim to moderate lighting brings out the best in their copper glow, it sounds counterintuitive, but these fish actually look more colorful under lower light because the copper pigmentation contrasts more sharply against the darker surroundings.

If you’re running higher-intensity lighting for demanding plants, use floating plants like water sprite, frogbit, or red root floaters to create shaded zones. The fish will naturally gravitate to these dimmer areas, and you’ll see their best color there.

Plants & Decorations

A well-planted tank is essential for getting the most out of copper rasboras. Dense planting along the sides and back provides security, while open areas in the center give the school room to swim together. Some excellent plant choices include:

• Cryptocoryne species: Thrive in the same soft, acidic water that copper rasboras prefer, and their broad leaves can serve as spawning sites
• Java fern and Anubias: Hardy, low-light epiphytes that attach to driftwood and provide structure
• Floating plants: Water sprite, frogbit, or salvinia to diffuse light from above
• Mosses: Java moss and Christmas moss draped over driftwood create a lush, natural look and provide cover
• Stem plants: Rotala, ludwigia, or hygrophila for background planting

Driftwood is highly recommended, both for the natural look and for the tannins it releases. Scattered Indian almond leaves on the substrate complete the blackwater biotope effect and provide surfaces for biofilm growth that the fish will graze on between feedings. If you want to see copper rasboras at their absolute peak, build a Southeast Asian blackwater biotope tank, it’s what they were made for.

Substrate

Dark substrate is the clear winner for this species. Dark sand, fine dark gravel, or aquasoil all work well. A dark bottom contrasts beautifully with the copper glow and mimics the leaf-litter-covered floors of their natural peat swamp habitat. Many planted tank substrates like ADA Amazonia or Fluval Stratum also buffer toward a slightly acidic pH, which is a bonus for these fish. Avoid bright white or light-colored substrates, which wash out their color and can make the fish feel exposed.

Tank Mates

Copper rasboras are gentle, peaceful fish that won’t bother anything in the tank. They’re also tiny and can’t defend themselves against anything remotely aggressive, so choosing compatible tank mates is important. The ideal companions are other small, calm species that share their preference for soft, acidic water.

Best Tank Mates

• Other rasboras: Chili rasboras, phoenix rasboras, emerald dwarf rasboras, harlequin rasboras
• Small tetras: Ember tetras, green neon tetras, neon tetras, cardinal tetras
• Corydoras catfish: Pygmy corys, habrosus corys, hastatus corys (the dwarf species are a perfect size match)
• Otocinclus catfish: Peaceful algae grazers that stay small and won’t compete
• Small gouramis: Sparkling gouramis, chocolate gouramis, licorice gouramis
• Dwarf shrimp: Cherry shrimp, amano shrimp (adult shrimp are safe; baby shrimp may be eaten)
• Kuhli loaches: Peaceful bottom dwellers that occupy a different zone
• Snails: Nerite snails, Malaysian trumpet snails, ramshorn snails

Tank Mates to Avoid

• Aggressive or semi-aggressive cichlids: Even small cichlids like rams can be too pushy for copper rasboras
• Tiger barbs and other nippy species: Will harass and stress these delicate fish
• Large or predatory fish: Anything that can fit a 1.25-inch fish in its mouth is a threat
• Bettas: Risky pairing. Some bettas will leave them alone, but aggressive males may target them. The rasboras’ small size makes them vulnerable.
• Fast, boisterous fish: Giant danios, Buenos Aires tetras, or other large active species will outcompete them for food and dominate the swimming space

Food & Diet

Copper rasboras are omnivores with very small mouths, so food size matters. In the wild, they feed on tiny insects, zooplankton, worms, and other small invertebrates. In captivity, they’re not fussy eaters, but you need to make sure the food is small enough for them to consume. Crushing or grinding standard flakes and pellets is often necessary.

A solid feeding plan for copper rasboras:

• High-quality micro pellets or finely crushed flakes as a daily staple, choose products with whole fish or insect meal as the first ingredient
• Frozen foods: Baby brine shrimp, daphnia, cyclops, and micro bloodworms are excellent. These boost color noticeably.
• Live foods: Baby brine shrimp, microworms, vinegar eels, and daphnia. Live foods trigger the strongest feeding response and are the best option for conditioning breeders.
• Freeze-dried foods: Daphnia and tubifex as an occasional treat, pre-soaked to prevent digestive issues.

Feed small amounts once or twice daily. These are tiny fish and it takes very little food to satisfy them. Aim for what the school can finish in 60 to 90 seconds. Overfeeding is the fastest way to foul the water in a small tank, and poor water quality is the number one health risk for this species.

Is the Copper Rasbora Right for You?

Before you add a Copper Rasbora to your tank, here is an honest assessment of what you’re signing up for. I’d rather you know exactly what to expect now than find out the hard way after you’ve already bought one.

• Experience level: Copper Rasboras are best suited for intermediate to advanced keepers. They have specific requirements that can overwhelm beginners.
• Tank size commitment: You’ll need at least 10 gallons, though bigger is always better. Make sure you have room for the tank before buying.
• Tank mate planning: Copper Rasboras can be territorial, so plan your community carefully. Not every fish will work as a tank mate.
• Maintenance demands: Expect regular water testing and consistent water changes. Copper Rasboras are sensitive to parameter fluctuations.
• Budget reality: Keeping Copper Rasboras costs more than typical setups. Budget for ongoing costs, not just the initial purchase.
• Time investment: Beyond daily feeding and weekly maintenance, regular observation is the best way to catch health issues early.
• Long-term commitment: With proper care, Copper Rasboras can live up to 5 years. Make sure you’re ready for years of consistent care.

Breeding & Reproduction

Breeding copper rasboras is possible in a home aquarium, but it requires more effort and attention to water chemistry than many beginner-friendly species. Like the other Trigonostigma species, copper rasboras have a unique spawning behavior, they deposit adhesive eggs on the undersides of broad leaves rather than scattering them randomly. This makes their breeding process more interesting to observe than a typical egg scatterer.

Breeding Difficulty

Moderate. Copper rasboras can be bred in captivity, but they require very specific water conditions, specifically very soft, acidic water, and a dedicated spawning setup. Don’t expect successful breeding in a community tank. Even if spawning occurs, eggs and fry will be quickly eaten by tank mates and the parents themselves.

Spawning Tank Setup

Set up a dedicated breeding tank of 5 to 10 gallons with the following:

• Dim lighting or heavy shading from floating plants
• Sponge filter set to the lowest possible flow
• Several broad-leaved plants. Cryptocoryne species and Anubias are ideal. The fish deposit eggs on the undersides of these leaves.
• Thin layer of dark substrate or bare bottom
• Cover the tank well and keep it in a quiet location away from foot traffic

Water Conditions for Breeding

Very soft, acidic water is non-negotiable for breeding copper rasboras. Target these parameters:

• Temperature: 78 to 82°F (26 to 28°C), slightly warmer than their normal range
• pH: 5.0 to 6.0
• Hardness: 1 to 4 dGH (extremely soft)

RO water remineralized with a very small amount of GH booster is the most reliable way to achieve these conditions. Adding Indian almond leaves or peat filtration helps achieve the low pH and provides tannins that seem to encourage spawning behavior.

Conditioning & Spawning

Condition your breeding group (ideally a small group with slightly more females than males) with generous portions of live and frozen foods for about two weeks before moving them to the spawning tank. Baby brine shrimp and daphnia are excellent conditioning foods. Well-conditioned females will become noticeably rounder when viewed from above.

Introduce the fish to the breeding tank in the evening. Spawning typically occurs during the morning hours. The male courts the female with a shimmering display, swimming alongside her. When the pair is ready, they move to the underside of a broad leaf. The female inverts and deposits adhesive eggs on the leaf surface while the male fertilizes them. The process repeats over several hours, producing roughly 20 to 50 eggs per spawning event, fewer than the larger harlequin rasbora, which reflects their smaller body size.

Egg & Fry Care

Remove the adults immediately after spawning is complete. They will eat the eggs if left in the tank. The eggs are tiny, translucent, and attached to the leaf undersides. They typically hatch in 24 to 48 hours depending on temperature.

The newly hatched fry are extremely small, even by rasbora standards, and will absorb their yolk sacs for the first day or two. Once free-swimming, start feeding infusoria or commercially available liquid fry food. After about a week, graduate to freshly hatched baby brine shrimp and microworms. Keep the water immaculately clean with very small, careful water changes. Growth is slow, and it may take several weeks before the fry begin to show any color. Be patient, raising T. hengeli fry is a rewarding but gradual process.

Common Health Issues

Copper rasboras are generally hardy little fish that aren’t prone to species-specific diseases. Most health problems trace back to poor water quality, stress, or unsuitable conditions. Here are the most common issues you may encounter:

Ich (White Spot Disease)

Ich is the most common freshwater fish disease and copper rasboras are susceptible, particularly when stressed by temperature swings or degraded water quality. Look for small white spots resembling grains of salt on the body and fins. Treat by gradually raising the temperature to 82 to 84°F (28 to 29°C) and using a half dose of ich medication. These small fish can be sensitive to full-strength chemical treatments, so err on the side of caution with dosing.

Fin Rot

Ragged, deteriorating fins are a sign of bacterial infection, almost always caused by poor water conditions. Mild cases often resolve with improved water quality through more frequent water changes. Advanced fin rot may need treatment with an antibacterial medication. Prevention is straightforward, keep the water clean and parameters stable.

Columnaris

This bacterial infection presents as white or grayish patches on the body, mouth, or fins and is frequently mistaken for a fungal infection. Columnaris is triggered by stress and poor water quality. Treatment typically requires an antibiotic like kanamycin or a product containing nitrofurazone.

Internal Parasites

If your copper rasboras are eating normally but losing weight, or if you notice white stringy feces, internal parasites may be the cause. This is more common in wild-caught specimens. Treat with medicated food containing levamisole or praziquantel.

The best medicine is prevention. Weekly water changes of 20 to 30%, avoiding overstocking, quarantining all new fish for at least two weeks, and maintaining stable parameters will prevent the vast majority of health problems with this species.

Common Mistakes to Avoid

• Keeping them in groups that are too small. A pair or trio of copper rasboras will be stressed, pale, and hide constantly. These are schooling fish that need at least 6, and 8 to 12 is much better. Their confidence, coloration, and schooling behavior all improve dramatically with larger group sizes.
• Hard, alkaline water. These fish evolved in some of the softest, most acidic water on the planet. Keeping them in water above pH 7.0 or above 10 dGH leads to washed-out color and chronic stress. If your tap water is hard, invest in an RO system or blend with RO water. The difference in color alone makes it worth the effort.
• Bright lighting without shade. Copper rasboras look their worst under intense, unshaded lighting. Their color washes out and they become skittish. Add floating plants and provide dimmer zones where they can retreat. Ironically, less light means more visible glow.
• Overfeeding. These are tiny fish with tiny appetites. It takes a surprisingly small amount of food to feed a school of copper rasboras, and uneaten food deteriorates water quality fast in small tanks.
• Mixing with aggressive or large tank mates. At 1.25 inches max, copper rasboras are bite-sized for many common aquarium fish. Choose companions carefully and stick to other nano species.
• Buying mislabeled fish. Copper rasboras, harlequin rasboras, and lambchop rasboras are frequently mixed up or mislabeled at fish stores. Always check the dark marking, if it’s a broad triangle, you’ve got harlequins, not hengelis. The copper rasbora has the thinnest marking of the three, almost a line, with that distinctive bright copper glow above it.

Where to Buy

Copper rasboras are less commonly stocked than harlequin rasboras at chain pet stores, but they’ve become increasingly available through specialty fish shops and online retailers as nano tanks and planted aquascaping have grown in popularity. Expect to pay around $3 to $5 per fish depending on the source and quantity.

For healthy, well-conditioned fish that have been properly quarantined before shipping, I recommend checking Flip Aquatics or Dan’s Fish. Both are reputable online retailers that consistently ship fish in great condition and are a significant step up from what you’ll typically find at big box pet stores. Buying online also makes it easier to get a larger group in one order, which is exactly what you want with a schooling species like this.

When selecting fish, look for active individuals with clear eyes, intact fins, and visible copper coloration. Avoid any fish that appear lethargic, have clamped fins, or show visible spots or patches. And take a close look at the body marking before buying, make sure you’re getting actual T. hengeli and not mislabeled harlequins or espei rasboras. The thin dark line with a bright copper glow above it is the giveaway.

Frequently Asked Questions

How many copper rasboras should I keep?

A minimum of 6, but 8 to 12 is ideal. Copper rasboras are a true schooling species that rely on group dynamics for security and natural behavior. Larger groups produce tighter schooling, bolder behavior, and visibly better coloration. In a small group of 2 or 3, they’ll be stressed, pale, and prone to hiding behind decor all day.

What’s the difference between copper rasboras and harlequin rasboras?

The copper rasbora (T. hengeli) is smaller, maxing out at 1.25 inches (3 cm) compared to the harlequin’s 2 inches (5 cm). The most obvious visual difference is the dark body marking: the harlequin has a broad, triangular wedge, while the copper rasbora has a much thinner dark line with a vivid copper-orange glow above it. The copper rasbora also has a more translucent body overall. Care requirements are similar, though copper rasboras generally prefer slightly softer and more acidic water.

Are copper rasboras good for nano tanks?

Yes, they’re one of the best nano schooling fish available. Their tiny maximum size of 1.25 inches (3 cm) makes them well-suited for 10 to 15-gallon planted nano setups. A group of 8 to 10 in a well-planted 10-gallon tank with soft water and dim lighting creates a genuinely impressive display. Just make sure the tank is fully cycled and the water stays clean, smaller tanks require more diligent maintenance.

Can copper rasboras live with shrimp?

Adult cherry shrimp and amano shrimp are generally safe with copper rasboras. The fish are small enough that even adult shrimp are far too large for them to bother. However, baby shrimp (shrimplets) may be picked off, as they’re small enough to fit in the rasboras’ mouths. If you’re breeding shrimp in the same tank, provide plenty of dense moss and plant cover to give the shrimplets hiding spots. It’s not a species that actively hunts shrimp, but opportunistic snacking on tiny shrimplets is a possibility.

Why are my copper rasboras losing their color?

Faded color in copper rasboras almost always comes down to one or more of these factors: water that’s too hard or alkaline (high pH or GH), overly bright lighting without enough shade, stress from a group that’s too small, or a bland diet lacking variety. Check your water parameters, add floating plants to create dimmer zones, make sure you have at least 6 fish, and incorporate frozen and live foods into their diet. Indian almond leaves or driftwood can help soften the water and add tannins that bring out their natural glow. When conditions are right, the transformation in color can be dramatic.

Do copper rasboras need a heater?

Yes. Copper rasboras are tropical fish that need a consistent temperature between 73 and 82°F (23 to 28°C). Unless you live in a climate where your home stays within that range year-round, a reliable aquarium heater is necessary. Temperature fluctuations stress these fish and make them susceptible to diseases like ich. A small, adjustable heater rated for your tank size is a worthwhile investment.

How the Copper Rasbora Compares to Similar Species

If you’re considering a Copper Rasbora, you’ve probably also looked at the Harlequin Rasbora. Both fill similar roles, but the differences matter when planning your tank. The Copper Rasbora has its own distinct personality and care needs. In my experience, the choice often comes down to the specific community you’re building and whether your water parameters favor one over the other.

The Lambchop Rasbora is worth considering as well. While the Copper Rasbora and the Lambchop Rasbora share some overlap in care, they bring different energy to a tank. If you have the space, keeping both in separate setups gives you a great chance to compare their behavior firsthand.

Closing Thoughts

The copper rasbora is one of those fish that consistently surprises people when they see it in person for the first time. Photos don’t do justice to that neon copper glow, it’s something you need to see under the right conditions to fully appreciate. In a dimly lit planted tank with soft, tannin-stained water and a dark substrate, a school of 10 or 12 T. hengeli looks like a collection of tiny glowing embers drifting through the midwater. It’s one of the most visually striking displays you can create in a nano aquarium.

They’re peaceful, small enough for modest-sized tanks, and not difficult to care for as long as you respect their preference for soft, acidic water. If you’ve kept harlequin rasboras before and enjoyed them, the copper rasbora is the next step, a smaller, more luminous relative that rewards a little extra attention to water chemistry with coloration you have to see in person. A photo never gets that copper glow right.

Recommended Video

Check out our rasbora video where we cover some of the most popular rasboras in the hobby, including the copper rasbora:

References

• Trigonostigma hengeli (Meinken, 1956) – FishBase
• Trigonostigma hengeli Profile – Seriously Fish
• Glowlight Rasbora Care Guide – Practical Fishkeeping

Table of Contents

• What Care Guides Get Wrong
• Key Takeaways
• Species Overview
• Classification
• Origin & Natural Habitat
• Appearance & Identification
• Average Size & Lifespan
• Care Guide
• Is It Right for You?
• Tank Mates
• Food & Diet
• Breeding & Reproduction
• Common Health Issues
• Common Mistakes to Avoid
• Where to Buy
• Frequently Asked Questions
• Species Comparison
• Closing Thoughts
• References

The scissortail rasbora is one of those fish that catches your eye from across the room. It’s bigger than most rasboras, topping out around 5 inches (13 cm), and it has this unmistakable caudal fin that opens and closes in a twitching, scissor-like motion as it swims. Once you notice it, you can’t unsee it. That little flicking movement is what earned Rasbora trilineata its common name, and it’s one of the most distinctive behaviors you’ll see in any freshwater schooling fish.

What Most Care Guides Get Wrong About the Scissortail Rasbora

The Scissortail Rasbora is one of the most underappreciated community fish in the hobby. The misconception is that it is a plain silver fish with no personality. Watch a school of 8+ in a large tank and you will change your mind fast. The scissoring tail motion is mesmerizing, and a tight school moving in unison is one of the best sights in freshwater fishkeeping. The mistake people make is keeping 3-4 in a 20-gallon tank, where they just look like stressed generic silver fish. This species needs numbers and space to shine.

Despite its larger size, the scissortail rasbora is a thoroughly peaceful community fish with a care level that suits beginners and experienced hobbyists alike. They’re hardy, they eat everything, and they look spectacular in groups of six or more zipping around the upper half of a well-planted tank. If you’ve been keeping smaller rasboras like harlequins or chili rasboras and you want something with more presence, the scissortail is a natural step up. Let’s walk through everything you need to know to keep them happy and healthy.

Key Takeaways

• One of the larger rasbora species, reaching up to 5 inches (13 cm), so they need a minimum 30-gallon tank with plenty of horizontal swimming space
• Named for their distinctive tail — the deeply forked caudal fin has black and yellow markings and twitches open and closed like a pair of scissors while the fish swims
• Excellent community fish that do well with similarly sized peaceful species, but they’re too large and active to pair with nano fish
• Keep in groups of 6 or more — they’re a true schooling species that looks best and behaves most naturally in a sizable group
• Active swimmers that appreciate some current — provide moderate water flow and open swimming areas in the middle and upper water column
• Known jumpers — a tight-fitting lid is essential, as these active swimmers will leap out of uncovered tanks
• Hardy and easy to care for with a wide tolerance for water parameters, making them a great choice for beginner community tanks

Species Overview

Field	Details
Scientific Name	Rasbora trilineata (Steindachner, 1870)
Common Names	Scissortail Rasbora, Three-lined Rasbora
Family	Danionidae
Origin	Southeast Asia (Thailand, Malaysia, Borneo, Sumatra)
Care Level	Easy
Temperament	Peaceful
Diet	Omnivore
Tank Level	Mid to Top
Maximum Size	5 inches (13 cm)
Minimum Tank Size	30 gallons (114 liters)
Temperature	73 to 78°F (23 to 26°C)
pH	6.0 to 7.5
Hardness	2 to 10 dGH
Lifespan	5+ years
Breeding	Egg scatterer
Breeding Difficulty	Moderate
Compatibility	Community
OK for Planted Tanks?	Yes

Classification

Taxonomic Level	Classification
Order	Cypriniformes
Family	Danionidae (formerly placed in Cyprinidae)
Genus	Rasbora
Species	R. trilineata (Steindachner, 1870)

The scissortail rasbora was first described by Franz Steindachner in 1870 as Rasbora trilineata, and that name has remained remarkably stable over the years. The species name “trilineata” translates to “three-lined,” referring to the faint horizontal lines running along the body. Unlike many other rasbora species that have been reclassified into new genera in recent years (like Trigonostigma for the harlequin rasboras), R. trilineata has stayed right where it was originally placed.

The family Danionidae itself was separated from the broader Cyprinidae in relatively recent taxonomic revisions, which is why you’ll still occasionally see older references listing scissortails under Cyprinidae. The current accepted classification places them in Danionidae, and that’s what you’ll find in modern databases.

Origin & Natural Habitat

Scissortail rasboras are native to Southeast Asia, with a range that covers Thailand, peninsular Malaysia, Borneo, and Sumatra. They’ve been collected across a wide area within these regions, inhabiting rivers, streams, and associated flood plains in lowland tropical forests. Their distribution spans the major river basins of Thailand, Malaysia, and Indonesia.

In the wild, they favor areas with moderate current, typically clear or slightly tannin-stained water flowing over sandy or gravelly substrates. They tend to occupy the middle and upper portions of the water column, staying in open water rather than hiding among dense vegetation. That said, they’re usually found near areas with some overhanging vegetation and submerged roots that provide cover when needed. The water in their natural habitats is generally soft and slightly acidic, though conditions can vary depending on the specific watershed and seasonal changes.

These are not fish from tiny, still jungle pools. They come from flowing environments with room to swim, which is an important detail to keep in mind when setting up their aquarium. If you want your scissortails to feel at home, think open water with some current rather than a densely planted, still-water setup.

Appearance & Identification

The scissortail rasbora has a streamlined, somewhat elongated body with a silvery base color that can show a subtle greenish or olive sheen under good lighting. It’s not the most colorful fish in the hobby by any means, but what it lacks in vivid pigment it makes up for with form and movement. The body is semi-translucent, and you can often see the outline of internal organs and the dark line of the gut, which is common among many rasbora species.

The defining feature, of course, is the tail. The caudal fin is deeply forked, with each lobe bearing a bold black bar tipped with yellow or white. When the fish swims, the lobes of the tail open and close in a rhythmic twitching motion that looks exactly like a pair of scissors snipping. It’s a constant, involuntary movement, and in a school of six or more fish, the effect of all those tails flicking in unison is surprisingly eye-catching.

The “three-lined” part of the name refers to faint horizontal lines that run along the body. The most visible is a dark midlateral stripe that extends from behind the gill cover to the base of the tail. Two additional lines, one above and one below, are often quite faint and may only be visible under certain lighting conditions or at specific angles. They’re more prominent in some individuals than others.

Male vs Female

Telling male and female scissortail rasboras apart isn’t always easy, but there are some clues once the fish are mature. Females tend to be slightly larger and noticeably deeper-bodied, especially when they’re carrying eggs. A gravid female will have a rounder, fuller belly compared to the more streamlined profile of a male. Males are generally a touch slimmer and may show slightly more vivid markings on the caudal fin, though this difference is subtle. There’s no dramatic color difference between the sexes, so body shape is your most reliable indicator.

Average Size & Lifespan

Scissortail rasboras can reach up to 5 inches (13 cm) in total length, making them one of the larger commonly kept rasbora species. In aquariums, most individuals top out around 4 to 4.5 inches (10 to 11 cm), but well-fed fish in spacious tanks can certainly hit the full 5-inch mark. This is a significantly bigger fish than popular rasboras like harlequins or lambchops, so plan your tank size accordingly.

With proper care, scissortail rasboras typically live 5 to 7 years in captivity. Some hobbyists have reported individuals reaching 8 years in ideal conditions. Clean water, a balanced diet, and a stress-free environment with appropriate group sizes all contribute to pushing them toward the upper end of that range. As with most fish, consistently poor water quality is the single biggest factor that shortens lifespan.

Care Guide

Tank Size

A 30-gallon tank is the minimum for a group of scissortail rasboras. This is a bigger requirement than most rasbora species, and it’s driven entirely by their size and activity level. These are strong, fast swimmers that spend most of their time cruising the middle and upper portions of the tank. In anything smaller than 30 gallons, they simply won’t have the room they need to swim comfortably, and you’ll see stunted growth and stressed behavior as a result.

If you can go bigger, do it. A 40-gallon breeder or a standard 55-gallon tank gives a school of 6 to 8 scissortails the kind of swimming space where they really shine. Prioritize horizontal swimming length over height. These fish want to cruise back and forth across the tank, not swim up and down. A long, shallow tank is better than a tall, narrow one.

Water Parameters

Parameter	Ideal Range
Temperature	73 to 78°F (23 to 26°C)
pH	6.0 to 7.5
Hardness	2 to 10 dGH
Ammonia	0 ppm
Nitrite	0 ppm
Nitrate	Below 20 ppm

Scissortail rasboras are quite adaptable when it comes to water chemistry. They do well across a range of pH values from slightly acidic to neutral, and they can handle both soft and moderately hard water without issues. The key, as with most freshwater fish, is consistency. Stable parameters matter more than hitting a perfect number. Keep ammonia and nitrite at zero, nitrates under 20 ppm, and maintain a regular water change schedule of 25 to 30% weekly. That’s really all it takes.

Filtration & Water Flow

This is where scissortail rasboras differ from a lot of other rasboras. They actually appreciate some current in the tank. In the wild, they come from rivers and streams with moderate flow, and they’re strong enough swimmers to handle it easily. A hang-on-back filter or canister filter that produces a noticeable but not overpowering flow across the length of the tank is ideal. You don’t want to turn the tank into a whitewater rapids situation, but a gentle to moderate current will keep your scissortails active and engaged.

Aim for a filter rated for your tank size or slightly above. Good mechanical and biological filtration is important, especially in a tank with a school of larger-bodied rasboras that produce more waste than their smaller cousins. If you’re running a canister filter, positioning the outflow to create a linear current from one end of the tank to the other gives the fish a natural flow pattern to swim against.

Lighting

Scissortail rasboras don’t have any special lighting requirements. Standard aquarium lighting suitable for growing live plants works perfectly. They come from environments with a mix of open water and shaded areas, so moderate lighting is ideal. If your lights are on the brighter side, providing some floating plants to create shaded zones gives them areas to retreat to when they want a break from the spotlight. A consistent photoperiod of 8 to 10 hours daily helps maintain a natural rhythm.

Plants & Decorations

The most important thing when decorating a scissortail rasbora tank is to leave plenty of open swimming space in the middle and upper portions of the tank. These are not fish that spend their time weaving through dense plant thickets. They want room to cruise. Plant around the perimeter and back of the tank, using taller stem plants like Vallisneria, Hygrophila, or Amazon swords to create a natural-looking backdrop, but keep the center of the tank relatively open.

Driftwood and smooth rocks can provide visual interest and break up sight lines without blocking swimming lanes. Floating plants like Amazon frogbit or red root floaters are a nice addition since they provide shaded areas and help diffuse light, mimicking the overhanging vegetation found in their natural habitats. Just make sure floating plants don’t completely cover the surface, as scissortails are mid-to-top swimmers that appreciate access to the upper water column.

Substrate

Substrate choice is not critical for scissortail rasboras since they spend almost no time near the bottom of the tank. Fine gravel, sand, or aquasoil all work equally well. If you’re keeping live plants, choose a substrate that supports plant growth. Dark-colored substrates tend to bring out the contrast of the fish’s silver body and black-marked tail, making them look more visually striking. But honestly, this is more of an aesthetic preference than a care requirement.

Is the Scissortail Rasbora Right for You?

Before you buy, run through this honest checklist. The Scissortail Rasbora is a great fish for the right keeper, but it is not for everyone.

• You have a 40-gallon or larger tank, preferably long rather than tall
• You can keep a school of 8+ for the signature synchronized swimming
• You want an active, fast-swimming schooler that uses the full length of your tank
• You enjoy motion and activity over static coloring
• Your tank has open swimming space with some planted areas for contrast
• You want a bulletproof species that adapts to most conditions

Tank Mates

Scissortail rasboras are peaceful schooling fish that get along with a wide range of community tank mates. Their size, however, means you need to think a little differently compared to picking companions for smaller rasboras. They do best with fish of a similar size and temperament.

Best Tank Mates

• Other medium rasboras — harlequin rasboras, brilliant rasboras, and similar mid-sized species
• Danios — giant danios and pearl danios make excellent companions given their similar size and activity level
• Barbs — cherry barbs, gold barbs, and odessa barbs are all good options. Avoid the nippier tiger barbs unless you keep them in large groups
• Tetras — larger tetras like black skirt tetras, Colombian tetras, or Congo tetras work well
• Corydoras catfish — any Corydoras species fills the bottom of the tank nicely while scissortails handle the upper levels
• Loaches — kuhli loaches, yo-yo loaches, and similar peaceful loach species
• Gouramis — pearl gouramis, honey gouramis, and dwarf gouramis are all compatible
• Rainbowfish — Boesemani, turquoise, or dwarf neon rainbowfish share a similar active swimming style
• Plecos and Otocinclus — bristlenose plecos and otos make good algae-eating companions
• Peaceful livebearers — larger platies and swordtails can work in the right setup

Tank Mates to Avoid

• Nano fish — chili rasboras, ember tetras, celestial pearl danios, and other tiny species may be stressed by the scissortail’s size and activity. While scissortails aren’t predatory, their constant fast swimming can overwhelm very small tank mates
• Small shrimp — adult cherry shrimp and Amano shrimp are generally safe, but baby shrimp may be picked off. If you’re running a serious shrimp breeding setup, scissortails aren’t the best choice
• Aggressive cichlids — Oscars, Jack Dempseys, and other large or territorial cichlids will bully or eat scissortails
• Slow, long-finned fish — while scissortails aren’t fin nippers, their fast, active swimming can stress out slow-moving species like fancy goldfish or long-finned bettas
• Very large predatory fish — anything big enough to fit a scissortail in its mouth should obviously be avoided

Food & Diet

Scissortail rasboras are unfussy omnivores that accept pretty much anything you offer them. In the wild, they feed on small insects, insect larvae, worms, zooplankton, and small crustaceans. In the aquarium, they’ll eagerly take a wide range of prepared and live foods.

A good quality flake food or micro pellet should form the staple of their diet. Supplement this regularly with frozen or live foods like bloodworms, daphnia, brine shrimp, and mosquito larvae. These protein-rich foods bring out better coloring and keep the fish in peak condition. Freeze-dried options work too, though frozen and live foods are nutritionally superior.

Feed once or twice daily, offering only what the school can consume in about two minutes. Scissortails are mid-to-top feeders and will grab food as it sinks through the water column. They’re not shy eaters and will be among the first fish to the surface at feeding time. Overfeeding is a bigger concern than underfeeding, as excess food quickly degrades water quality in any tank. A fasting day once a week doesn’t hurt, either.

Breeding & Reproduction

Breeding scissortail rasboras in captivity is possible but requires some dedicated effort. They’re egg scatterers that show no parental care, and they’ll eat their own eggs if given the chance. Most successful breeding happens in a separate spawning tank rather than in the main community setup.

Breeding Difficulty

Moderate. Scissortail rasboras are not as easy to breed as zebra danios or some other cyprinids, but they’re far from impossible. The main challenges are getting the water conditions right, conditioning the adults properly, and separating eggs from the parents quickly enough. If you’ve successfully bred other rasboras or egg-scattering species, you’ll have a head start.

Spawning Tank Setup

Set up a separate breeding tank of at least 20 gallons. Cover the bottom with a layer of glass marbles or a mesh screen that allows eggs to fall through but prevents the adults from reaching them. This is critical because scissortails will eat every egg they can find. Include some fine-leaved plants like Java moss or spawning mops to give the fish additional egg-scattering sites. Gentle filtration from a sponge filter provides water movement without pulling in eggs or fry.

Water Conditions for Breeding

Slightly warmer, softer water tends to trigger spawning behavior. Raise the temperature to around 79 to 82°F (26 to 28°C) and aim for a pH of 6.0 to 6.5 with soft water in the 2 to 5 dGH range. Some breeders use RO water mixed with a small amount of tap water to achieve these conditions. Morning sunlight hitting the tank or a gradual increase in lighting can also serve as a spawning trigger.

Conditioning & Spawning

Condition breeding pairs or small groups with plenty of high-protein live and frozen foods for one to two weeks before attempting to spawn them. Bloodworms, daphnia, and brine shrimp are all excellent choices. Well-conditioned females will appear noticeably rounder as they fill with eggs.

Introduce the conditioned fish to the spawning tank in the evening and allow them to settle overnight. Spawning typically occurs in the early morning hours. The males will display for the females, and the pair will scatter adhesive and semi-adhesive eggs among the plants and across the substrate. A single spawning can produce several hundred eggs. Remove the adults immediately after spawning is complete to prevent them from eating the eggs.

Egg & Fry Care

Eggs typically hatch within 24 to 48 hours at breeding temperatures. The fry will remain attached to surfaces or lie on the bottom, absorbing their yolk sac for another two to three days before becoming free-swimming. Keep the breeding tank dimly lit during this stage, as the eggs and young fry are sensitive to strong light.

Once free-swimming, the fry need very small food. Infusoria and commercially prepared liquid fry food are good first foods for the initial week. After that, you can transition to freshly hatched baby brine shrimp and microworms. Growth is steady but not rapid. Maintain excellent water quality with gentle daily water changes of about 10%, being careful not to siphon up fry. As the fry grow, gradually introduce finely crushed flake food alongside live foods.

Common Health Issues

Scissortail rasboras are generally robust fish that don’t suffer from species-specific diseases. Most health issues that arise are the same ones that can affect any freshwater tropical fish and are typically triggered by poor water quality, stress, or introduction of sick fish without quarantine.

Ich (White Spot Disease)

Ich is the most common disease you’ll encounter with any freshwater fish, and scissortails are no exception. It presents as small white spots scattered across the body and fins, often accompanied by flashing (scratching against objects) and clamped fins. The good news is that it’s very treatable. Raising the temperature to 82 to 86°F (28 to 30°C) for 10 to 14 days speeds up the parasite’s life cycle, and standard ich medications containing malachite green are effective. Scissortails tolerate these treatments well.

Fin Rot

Fin rot shows up as frayed, discolored, or deteriorating fin edges, and it’s almost always caused by poor water quality or stress. In scissortails, the distinctive caudal fin is often the first place you’ll notice it. Improving water conditions through more frequent water changes is often enough to reverse mild cases. For more advanced fin rot, antibacterial treatments may be necessary. Catching it early is key, because a damaged caudal fin takes away the scissortail’s most distinctive visual feature.

Columnaris

Columnaris is a bacterial infection that can cause white or grayish patches on the body, mouth, or fins. It’s sometimes confused with a fungal infection because of its cotton-like appearance. Columnaris tends to strike when fish are stressed due to overcrowding, poor water quality, or temperature instability. Treatment involves antibacterial medications, and improving overall tank conditions is essential to prevent recurrence.

General Prevention

The best medicine is prevention. Quarantine all new fish for at least two weeks before adding them to your main tank. Maintain consistent water parameters with regular 25 to 30% weekly water changes. Avoid overstocking, keep up with filter maintenance, and feed a varied diet. Scissortail rasboras are tough fish, and in a clean, well-maintained tank, disease is rarely an issue.

Common Mistakes to Avoid

• Keeping them in too small a tank. This is the number one mistake with scissortail rasboras. A 10- or 20-gallon tank might work for harlequin rasboras, but scissortails grow to 5 inches (13 cm) and are highly active swimmers. They need at least 30 gallons, and bigger is always better. Cramped conditions lead to stunted growth and increased stress.
• Not keeping enough of them. Scissortails are schooling fish that need a group of at least 6. Keeping just 2 or 3 results in nervous, skittish behavior and washed-out coloring. In a proper school, they’re confident, active, and display their best fin movement.
• Pairing them with nano fish. Because scissortails are often labeled simply as “rasboras,” some hobbyists assume they can go in the same tank as chili rasboras or other micro species. The size and speed difference is too much. Nano fish can become stressed by the scissortail’s constant fast swimming.
• No lid on the tank. Scissortail rasboras are capable jumpers, especially when startled or during active feeding. A tight-fitting lid is strongly recommended to prevent losses.
• Too little swimming space. Filling the entire tank with dense plants and decorations leaves no open water for these fish to do what they do best — swim. Leave the center of the tank open and plant around the edges.
• Neglecting water flow. Unlike some rasboras that prefer still water, scissortails come from flowing environments and appreciate some current. A tank with zero water movement isn’t ideal for this species.

Where to Buy

Scissortail rasboras are regularly available at many local fish stores, though they’re not quite as universally stocked as zebra danios or neon tetras. You may need to ask your local shop to order them in, or you can look online. They’re usually priced around $3 to $6 per fish, and you’ll want to buy a group of at least 6 at once to establish a proper school from the start.

For healthy, well-conditioned stock shipped directly to your door, I’d recommend checking Flip Aquatics or Dan’s Fish. Both are reputable online retailers that quarantine their fish and ship in excellent condition. The quality tends to be a step above what you’ll find at chain pet stores, and online retailers are often more consistent about having scissortails in stock compared to local shops that may only carry them occasionally.

Frequently Asked Questions

How many scissortail rasboras should I keep together?

Keep a minimum of 6, and more is always better if your tank can support it. In groups smaller than 6, scissortails tend to be skittish and hide more often. A school of 8 to 10 in a 40-gallon or larger tank is where they really start to look impressive, with coordinated schooling behavior and confident movement throughout the tank.

Can scissortail rasboras live with bettas?

It’s not an ideal pairing. Scissortail rasboras are large, active swimmers that prefer moderate current and lots of swimming space. Bettas, on the other hand, prefer calm, still water and can be stressed by fast-moving tank mates. The scissortail’s constant motion is likely to agitate a betta. You’re better off pairing bettas with slower, calmer species and keeping your scissortails with tank mates that match their energy level.

Why is my scissortail rasbora’s tail twitching?

That’s completely normal and is the defining behavior of the species. The “scissor” motion of the caudal fin is a natural, constant movement that happens whenever the fish swims. It’s not a sign of illness, stress, or irritation. In fact, it’s the exact reason they got their common name. If you notice the tail twitching has stopped or the fish is clamping its fins against its body, that would actually be the cause for concern.

Are scissortail rasboras jumpers?

Yes, they can be. While they’re not as notorious as zebra danios or hatchetfish when it comes to jumping, scissortail rasboras are fast, active swimmers that can and will leap out of uncovered tanks, especially if startled by sudden movements or loud noises. Always keep a secure lid on the tank to be safe.

What’s the difference between scissortail rasboras and other rasbora species?

The biggest differences are size and behavior. At 5 inches (13 cm), scissortails are significantly larger than popular rasboras like harlequins at 2 inches (5 cm) or chili rasboras at under 1 inch (2 cm). They’re also more active and prefer tanks with some water flow, whereas many smaller rasboras do well in calmer conditions. Their distinctive scissoring tail motion is unique to this species and makes them easy to identify at a glance.

Do scissortail rasboras eat plants?

No. Scissortail rasboras are perfectly safe in planted tanks. They’re omnivores that feed primarily on small invertebrates and prepared foods, and they have no interest in eating or uprooting live plants. You can keep them with any aquarium plants without worry.

How the Scissortail Rasbora Compares to Similar Species

Scissortail Rasbora vs. Giant Danio

Both are large, active schoolers that need long tanks and big groups. The Giant Danio is more colorful but can be more boisterous. The Scissortail Rasbora has a more elegant swimming style with its signature tail movement. Both need 40+ gallons and are excellent for active community tanks.

Scissortail Rasbora vs. Brilliant Rasbora

The Brilliant Rasbora has better iridescent coloring, but the Scissortail Rasbora has more dynamic swimming behavior. Both are medium-sized, peaceful schoolers. The Scissortail Rasbora is the better choice if you prioritize movement and activity over coloring.

Closing Thoughts

The scissortail rasbora might not have the flashy neon colors of some other popular aquarium fish, but it has something a lot of those fish don’t: presence. A school of scissortails cruising through the upper half of a well-set-up tank, with all those forked tails snipping away in unison, is genuinely one of the more striking sights in the freshwater hobby. They’re big enough to hold their own in a community tank, peaceful enough to get along with almost everyone, and hardy enough that beginners can keep them without stress.

Give them room to swim, keep the water clean, maintain a proper school, and these fish will reward you with years of active, engaging behavior. If you’re looking for a rasbora that brings more size and movement to the table, the scissortail is hard to beat.

Looking for more rasbora and danio species to explore? Check out our full Rasboras & Danios: Complete Species Directory for care guides on all the most popular species in the group.

Recommended Video

Check out our rasbora video where we cover the most popular rasboras in the hobby:

References

• Rasbora trilineata (Steindachner, 1870) — FishBase
• Rasbora trilineata Profile — Seriously Fish
• Scissortail Rasbora Care Guide — Practical Fishkeeping