Chili Rasbora – Ultimate Care Guide

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The chili rasbora, AKA mosquito rasbora (Boraras brigittae) is an amazing little nano fish. More and more fish keepers have crossed over to the nano side of the hobby because of the diversity of species you can keep in a limited amount of space. When choosing a nano species, the chili rasbora has it all – great personality, and awesome looks, all packed into less than an inch!

Read on to learn everything you need to know about chili rasbora care, and setting up a great fish tank for them too!

Species Overview

Scientific NameBoraras brigittae
Common NamesChili rasbora, Mosquito rasbora
OriginBorneo, Southeast Asia
Care LevelModerate
Lifespanup to 8 years
Tank LevelMidwater
Minimum Tank Size5 gallons (10G recommended!)
Temperature Range70 ° to 82 °F
Water Hardness3 to 12 dkH
pH Range4 to 7
Filtration/Water FlowLow
Water TypeFreshwater
BreedingEgg layer
Difficulty to BreedModerate
CompatibilityCommunity tanks
OK, for Planted Tanks?Yes

Origins and Habitat

Chili rasboras are native to Borneo in Southeast Asia. Their natural habitat consists of pools in blackwater streams with extremely soft, and quite acidic water.

The water is often full of aquatic and floating plants and partially shaded by the forest trees above. Plenty of leaf litter accumulates in the water and stains it a dark color, creating quite a dim environment.

The chili rasbora (Boraras brigittae) is the most popular of a few closely related Boraras species. If the word ‘boraras’ sounds a little fishy, that’s because it’s an anagram of the word r-a-s-b-o-r-a. Who says fish scientists aren’t fun?

What Do They Look Like?

What Does A Chili Rasbora Look Like

The chili rasbora (Boraras brigittae) is a tiny nano fish with bold looks. The first impression when seeing this species is a very small, reddish fish with bold markings and huge eyes.

The males have deeper color but are smaller and more slender than the females, which also have rounder bellies. Dominant male chili rasboras become especially colorful, turning a deep red shade.

There is a characteristic black stripe on the sides of the fish’s body which can shine blueish green in good light. Just above this black stripe, you’ll notice a bright red or orange line.

Another stand-out feature is the red patch on the fish’s gill plate. This makes these nano schooling fish look like they have rosy cheeks!

To top it off, chili rasboras have great-looking fins. The base of their tail, and their dorsal and anal fins also have black and orange spots and markings.

How Big Are They?

If you thought something like a neon tetra or a guppy was small, just wait until you meet the chili rasbora! Chili rasboras are one of the smallest fish in the hobby, maxing out at less than an inch in total length.

In fact, a full-grown adult will only reach about 0.8 inches with good care. The male chili rasbora is slightly smaller and slimmer in build than the female.

How Long Do They Live?

Chili rasboras have a surprisingly long lifespan for such a small fish. In the right conditions, these hardy fish can live for up to 8 years!

To keep your fish living longer, make sure you provide them with a healthy and varied diet, a comfortable tank setup, and perform regular maintenance to keep your water quality pristine.

Temperament And Activity Level

The chili rasbora can be a pretty outgoing and confident little fish if kept in the right kind of tank setup. With larger fish as tank mates, however, chili rasboras can be very timid fish.

They spend most of their time up around the middle and top levels of the aquarium, but they can be seen just about anywhere too. The chili rasbora is known as a schooling fish and they are very social, although they won’t always group tightly.

Chili rasboras are very peaceful fish, so you don’t need to worry about them picking on any other fish in a community tank.

What Are Good Tank Mates?

The chili rasbora is a tiny fish, which can make choosing suitable tank mates a little challenging. Many fish keepers prefer to keep chili rasboras in species-only aquariums because they work so great in schools in nano tanks.

These fish will get along with most other peaceful fish, however, as long as they are not big enough to eat your rasboras.

Read on to learn more about the best (and worst) tank mates for chili rasboras.

Best Tank Mates

The best tank mates for chili rasboras are other peaceful nano fish. Let’s take a look at some of the best tank mates for these amazing fish:

Least Compatible Fish

Chili rasboras are so small that many of the most popular tropical aquarium fish could potentially swallow them whole. As a general rule, avoid keeping them, with anything over about 2.5 inches long.

You’ll also want to avoid any predatory fish, aggressive fin-nippers, and boisterous species that could outcompete them for food.

Here are a few common aquarium fish that will not make good tank mates for chili rasboras:


The chili rasbora is one of the safest fish to keep with dwarf shrimp. That being said, they are micro-predators so they will feed on tiny baby shrimp that have just hatched. If you plan on breeding your shrimp, a shrimp-only setup would be wiser.

Here are some shrimp that you can keep with the chili rasbora:

You can also keep snails with your chili rasboras. Snails do a terrific job of keeping an aquarium clean, but some species can really multiply fast. Nerite snails are a great choice because they look amazing, eliminate algae, and best of all, they won’t breed in your fish tank!

What Do They Eat?

The Chili rasbora is a micro predator that feeds on tiny insects and bugs. The name mosquito rasbora is probably a good clue as to what these tiny fish love to feed on in nature.

Think small when looking for food for these fish. They will do great on a diet of fish flakes and nano pellets, but supplementing with live/frozen foods will bring out the best condition and color in these nano fish. A good micro pellet formula is Xtreme Aquatics Foods Nano.

Great For Nano Fish
Xtreme Aquatic Foods Nano

Xtreme Aquatics Nano formula is specially designed for smaller fish and contained a well balance mix of raw ingredients. It is a great staple food for your nano fish.

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Let’s take a look at some of the types of food you can feed the chili rasbora:

Prepared Foods

  • Crushed flakes
  • Micro pellets

Live & Frozen Foods

  • Daphnia
  • Tubifex
  • Chopped bloodworms
  • White worms
  • Micro worms
  • Mosquito larvae
  • Baby brine shrimp

How Much And How Often To Feed Your Fish

Chili rasboras need to be fed regularly, at least once a day. It is better to feed these tiny fish small amounts two or three times a day, however.

The chili rasbora is often kept in nano tanks as small as 5 gallons, but this makes overfeeding especially dangerous. A bunch of uneaten food in such a small volume of water can cause dangerous ammonia spikes.

So how do you know how much to feed your fish?

When you go to feed your chili rasboras, watch them eat- they should finish all the food in just a minute or two. Feeding them this amount 2 or 3 times a day is a great way to keep your fish well-fed, without creating too much waste.

Setting Up Your Fish Tank

The chili rasbora (Boraras brigittae) is right at home in a nano tank. They do best in a planted tank with a dark substrate and low water flow. Chili rasboras love live plants, and floating types are a great choice.

Read on to learn more about how to set up a great chili rasbora tank!

Tank Size

The chili rasbora is one of the smallest freshwater fish in the aquarium trade, so they make a great choice for fish keepers who don’t have a lot of space.

A small group of these nano fish can thrive in tanks as small as 5 gallons. This would be the minimum tank size, however, and if you’re new to fish keeping, I’d recommend a larger tank like a 10 or 15-gallon.

Remember, the smaller an aquarium, the faster things can go wrong, so go slightly bigger to be on the safe side. A ten-gallon tank, for example, will be easier to maintain and allow you to keep an awesome little school of about 20 of these fish quite safely.


Chili rasboras do really well in a planted aquarium. Not only will your fish feel more at home between the leaves and roots, but live plants also have a number of great benefits when it comes to maintaining the high water quality these fish need.

If you’re not already a planted tank enthusiast, consider picking up some common and easy to grow species like:

These aquarium plants don’t need much maintenance and they won’t take over your tank too fast. Down the road you can look at improving your lighting, picking up some aquascaping tools, and investing in a CO2 injection system. I must warn you though, that the planted aquarium hobby can be addictive!

Go ahead and browse through some of the great plant care articles on this website to learn more about specific species and their care.


Chili rasboras look (and feel) their best when kept over a dark substrate. You can use a fine gravel or sand substrate as long as it is well rinsed and aquarium safe. If you plan on setting up a heavily planted tank, an aquarium soil would be a great option.


Chili rasboras like plenty of structure in their environment where they can hide out from predators. Fine driftwood like spider wood is great because it mimics the tangled roots and branches these fish are used to in their natural habitat.

Water Quality

The chili rasbora is actually really adaptable to a wide range of parameters, but they do require good water quality. They should never be added to an uncycled aquarium or kept in a tank with unstable or poor water quality. Consider doing a fishless cycle to make sure you start on the right foot.


Filtration is vital because the chili rasbora requires, stable, high-quality water with zero nitrites and ammonia. This means your aquarium needs to be cycled before you introduce your fish.

If you’re not sure how to cycle a new aquarium, go ahead and check out my article on aquarium cycling to learn everything you need to know about this vital step!

The type of filter you choose is not that important as long as it is a good size for your tank. The most important factor to consider is that chili rasboras are tiny and they will get blown around in a strong current. They can also be sucked into strong filter intakes, so you might want to choose a model that has a prefilter sponge.

Water Parameters

The chili rasbora prefers a water temperature anywhere between 70°F and 82°F, with something around the middle of this range probably being ideal. Use a heater to keep the temperature stable in your tank.

These fish prefer soft water that is slightly acidic. Aim for the following parameters:

  • pH: 4-7
  • GH: 1-2
  • KH: 3-12dKH

The chili rasbora needs really good water quality in order to thrive. Your water test results should always read zero ammonia, zero nitrite, and less than 20 ppm nitrates.

Aquarium Maintenance

Regular aquarium maintenance is the only way to keep nano tanks clean and safe for your fish. Performing a partial water change of 20-30% per week is a good way to keep nitrate levels in a safe range.

Be sure to remove any dead or dying plant matter, and suck up the dirt and waste that accumulates on your substrate with a gravel vacuum. If necessary, you can also rinse out your filter sponge media in the water you have just taken out of the tank. Remember to look after those precious beneficial bacteria!

Your tap water probably contains chemicals like chlorine or chloramine that are added to keep the water safe for human use. Unfortunately, these chemicals are toxic to fish, so make sure you use a water conditioner to neutralize the harmful effects.


The only way to know for sure if your maintenance schedule is appropriate is to test your aquarium water. Get yourself a test kit that can measure the following parameters:

  • Ammonia
  • Nitrite
  • Nitrate
  • pH
  • GH
  • KH

Test kits are really easy (and fun) to use. They work either by adding a drop of solution to some aquarium water in a test tube or by simply dipping a strip into your tank. All you need to do next is watch for the solution or strip to change color, and compare the results with the provided chart.

You should test your aquarium water before introducing your fish. This way you will know what your pH and water hardness are out of the tap.

If your tap water pH and hardness are too high, you might need to look at using rainwater or RO water in your tank. Avoid using distilled water that is not remineralized.


Breeding rasboras at home is a fun hobby that anyone can do with the right knowledge. Building up a big school can be a slow process, however, because these tiny fish only lay a few eggs at a time. Here is a wonderful video above by Mark’s Aquatics that goes into great detail. I have a few summary points below. Here’s what you need to know:


Before you can breed these fish, you’ll need to make sure you have both males and females. The female chili rasbora grows a little larger than the males and will also have a rounder belly. Dominant male chili rasboras tend to turn a bright and deep shade of red.

How They Breed

The chili rasbora is an egg-scattering fish that doesn’t show any parental care. This means they won’t look after their eggs or fry. If your fish are happy in their tank and in good condition, they will probably start breeding on their own and you might even spot some babies after a while.

If you want to breed this species in a more controlled way, you’re going to want to set up a separate breeding tank. The breeding tank only needs to hold 3 gallons or so, and a small sponge filter will work great for aerating the water and maintaining water quality.

Conditioning And Breeding Your Fish

Start by feeding your fish high-quality foods like micro worms and brine shrimp for a few days to bring them into peak condition.

Next, add some well-conditioned adults to your breeding tank and if they are happy, the female chili rasbora should lay eggs after a day or so. Remove the breeding fish and the eggs will start to hatch after about 2 days.

Raising Fry

Chili rasbora fry need to be fed from their second day after hatching. They can be fed a diet of infusoria. The fry are very small after hatching, so wait at least a week before doing a water change to avoid sucking them up by accident.

Health & Disease

The chili rasbora is known to be hardy fish, but like any species, they can be affected by various health problems. Read on to learn how to evaluate your fish’s health, and which problems to look out for.

Evaluating Your Their Health

Whether you’re picking out fish down at your local fish store, or just keeping an eye on the health of your pets at home, knowing what to look out for is really important. Healthy chili rasboras are:

  • Active
  • Colorful
  • Able to swim right side up, without floating or sinking

Unhealthy chili rasboras can show the following warning signs:

  • Rapid breathing
  • Floating, sinking, or swimming upside down
  • Flashing and rubbing their sides on the substrate
  • White spots on the body
  • Bulging eyes
  • White stringy feces
  • Bloating

Common Health Issues And Treatment

Aquarium fish can get sick for a number of reasons. The most common causes are infections from fungi, bacteria, viruses, and parasites. They can also suffer from physical injuries of course.

Infections can come in with new fish or plants, so it’s important to quarantine before adding them to your tank. Fish that are comfortable in their environment have a much smaller chance of getting sick than fish that are under stress, so always look for the root cause when any fish gets ill.

Here are some possible health issues (and their treatment) that your chili rasboras could develop:

  • Ich– Treat with medication or salt
  • Columnaris- Treat with antibiotics, medication, or salt
  • Fin rot– Treat with antibiotics or salt
  • Pop-eye- Treat with Epsom salts

Whenever you are unsure, check my post about fish diseases and consult a veterinarian for more advice. A best practice is to quarantine your fish prior to putting them into a display tank. It’s more common with saltwater tanks, but it is also done in freshwater tanks, especially planted aquariums.

Where To Buy

Chili rasboras are popular fish that are available from many local pet and fish stores. There are a few very similar-looking species in the hobby though, so make sure you’re getting genuine chili/mosquito rasboras.

If you can’t find any chili rasboras locally, or just prefer the convenience of online shopping, these fish are available from a number of trusted online retailers.


How many should be kept together?

The chili rasbora is a social schooling fish that should always be kept in groups. A minimum number of 6 or so is recommended, but 20 or more would be much better.

Are they hardy?

The chili rasbora is adaptable to a wide range of water parameters but they do require excellent water quality. They are very small fish, so it is best to acclimate them slowly when introducing them to your tank.

How big do they get?

The chili rasbora is a truly tiny species. They reach a maximum size of about 0.8 inches, but they might be as small as 0.25 inches when you buy them!

What fish can live with them?

The chili rasbora can live with other freshwater fish in a community tank. Compatible tank mates include peaceful fish like otocinclus catfish, pygmy corydoras, and other fish that stay small. Avoid larger fish that could eat your chili rasboras or outcompete them for food.

Can they live alone?

Chili rasboras should never be kept alone because they are naturally social schooling fish. It is best to keep them in a nice big school, the bigger the better!

Do they need plants?

Chili rasboras don’t necessarily need plants to survive but they will be much happier in a heavily planted tank because this is similar to their natural habitat.

Final Thoughts

Chili rasboras (Boraras brigittae) are one of the smallest tropical fish in the hobby. These stunning little fish are the perfect choice for fishkeepers who want a large number of fish but don’t have much room. Follow the tips in this guide to set up a great tank for your chili rasboras, and keep them happy and healthy.

Do you keep chili rasboras in your fish room? Tell us about your nano setup in the comments below!


  1. Hi Mark,

    solid guide there but what really irks me is that you put 5Gs as the minimum tank size. For sure many sellers and otherwise profit incentivised care sheets do nowadays put 5Gs as the minimum tank size but it is just super inappropriate for that species. Many good guides recommend minimum a 10G tank, as you kind of do yourself in the article here.

    They really should not be recommended to be below a shoal size of 10 and a tank size of 10Gs, as so many people lose a couple of them in the first days anyway.

    I’d appreciate if you would follow the more scientific and species-appropriate recommendations here for minimum recommendations and would happily link and include your article in that case on the biggest Boraras community.

    Btw. it should probably also be mentioned that they really should only be transferred and introduced to a well matured tank (no fish in cycling) and slowly and carefully acclimatized.


    • This could certainly be debated. Especially since I follow a more hobbyist approach and regularly get together with other influencers like KG Tropicals (Yes, I’m a real person in the hobby!), who have had success with Chili Rasboras in 5 gallons as an alternative to a sole Betta fish. I am more comfortable with placing schools of fish in 10 gallon tanks over a 5 gallon, but know that of all the schooling fish in the hobby, Chili and Exclaimation Point Rasboras are going to be one of the best for that tank size.

      That being said, I typically recommend a sole betta for any other fish when it comes to 5 gallon aquariums. As for cycling a tank, I am a proponent of fishless cycling. I’ve been fishless cycling since my early days in reefing since I was a teenager (over 20 years ago). I’ll add it to the article. I have a few articles on accumulation and quarantining (I was the one of first YouTubers on the internet to discuss quarantining marine fish along with Humble Fish). I’ll add those links as well. Sometimes I forget to add them in the articles :).


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