Last Updated: May 16, 2026
Thank you for visiting! By the way… any links on this page that lead to products on Amazon and other stores/partners are affiliate links Aquarium Store Depot earns a commission if you make a purchase.
Black fish do something colorful fish can’t. They create contrast. A single black ghost knifefish gliding through a planted tank at night is more striking than a dozen neon tetras. I’ve kept black mollies, black skirt tetras, and black ghost knifefish over the years, and there’s something genuinely arresting about a well-designed dark tank. But here’s what most list articles won’t tell you: half of these fish don’t belong in a beginner’s setup. Color is not a care level. This list ranks them honestly, from genuinely easy to genuinely expert-only.
Black fish are sold on aesthetics. They’re bought for the wrong tanks. Know what you’re getting into before you buy.
EXPERT TAKE | MARK VALDERRAMA
After 25 years in this hobby and time running aquarium stores, I’ve watched people impulse-buy black ghost knifefish and black arowanas because they look cool. Both fish end up in undersized tanks within weeks. The black fish that actually belongs in your community tank is the black molly or black neon tetra. The ghost knife and arowana are showpiece commitments, not additions. If you don’t have a 100-gallon plan, skip them entirely.
Quick Comparison Table
TIER BREAKDOWN
Beginner: Black Molly, Black Neon Tetra, Black Phantom Tetra
Intermediate: Black Skirt Tetra (in proper groups), Black Moor Goldfish, Red-Tail Black Shark
Advanced: Black Ghost Knifefish, Black Arowana
Key Takeaways
- True black coloration is rare in freshwater fish. Most “black” fish are dark gray, charcoal, or dark brown with black markings.
- Difficulty varies enormously across this category. Black mollies are beginner-friendly. Black arowanas are expert-only. Don’t group them together.
- The black ghost knifefish is one of the most impressive freshwater fish you can own, but it is not a beginner fish and requires a mature, well-established tank over 100 gallons (378 L).
- Black moor goldfish need cold water. They don’t belong in a tropical community setup, no matter how tempting the contrast looks.
- Black skirt tetras are fin nippers. Group size matters. A school of 8 or more reduces nipping behavior significantly.
Freshwater Black Fish Species
1. Black Molly
- Scientific Name: Poecilia sphenops
- Difficulty Level: Beginner
- Adult Size: 3 inches (7.5 cm)
- Minimum Tank Size: 20 gallons (75 L)
- Temperature: 70-80°F (21-27°C)
- pH: 7.0-8.5
- Temperament: Peaceful
- Diet: Omnivorous
The black molly is the most beginner-friendly fish on this list, and it’s genuinely black, not just dark. Jet black body, no reflective sheen, true color through and through. I’ve kept them in community tanks, species tanks, and brackish setups over the years. They’re adaptable and tolerant of a wide range of water conditions.
One thing most guides skip: black mollies do better with a small amount of aquarium salt in the water. Not brackish levels, but a teaspoon per 5 gallons (19 L) reduces stress and improves long-term health. They’re livebearers, so you’ll have fry if you keep males and females together. Plan accordingly.
What you get wrong with mollies: buying a 10-gallon (38 L) tank and crowding them. They need swimming room and consistent water quality. Small tanks crash faster, and mollies show stress quickly through fin clamping and lethargy.
2. Black Neon Tetra
- Scientific Name: Hyphessobrycon herbertaxelrodi
- Difficulty Level: Beginner
- Adult Size: 1.6 inches (4 cm)
- Minimum Tank Size: 10 gallons (38 L)
- Temperature: 73-81°F (23-27°C)
- pH: 5.5-7.5
- Temperament: Peaceful schooler
- Diet: Omnivorous
Despite the name, the black neon tetra is not a neon tetra. Different genus, different temperament, different care. It’s actually hardier than the neon and easier to keep. The black band running the length of the body is bold and graphic, especially against light substrate or green plants.
Keep them in groups of 8 or more. In a school of 6, they’re decent. In a school of 12, they’re spectacular. Black neons are one of the most underrated schoolers in the hobby and they work in tanks that neons would struggle in.
3. Black Phantom Tetra
- Scientific Name: Hyphessobrycon megalopterus
- Difficulty Level: Beginner
- Adult Size: 1.75 inches (4.5 cm)
- Minimum Tank Size: 10 gallons (38 L)
- Temperature: 72-82°F (22-28°C)
- pH: 6.0-7.5
- Temperament: Peaceful with mild male-male displays
- Diet: Omnivorous
The black phantom tetra is one of the most underrated fish on this list. Males display against each other with extended fins in a slow-motion standoff that looks almost choreographed. Nobody gets hurt, but the behavior is genuinely interesting to watch. The black spot behind the gill and dark body coloration make them visually distinct.
They do well in soft, slightly acidic water, but they’re tolerant of a wider range than most tetras. If you want something with visual interest and actual behavior beyond “swim in circles,” black phantoms deliver. Keep them in groups of 6 or more for best results.
4. Black Skirt Tetra
- Scientific Name: Gymnocorymbus ternetzi
- Difficulty Level: Beginner to Intermediate
- Adult Size: 2.5 inches (6 cm)
- Minimum Tank Size: 15 gallons (57 L)
- Temperature: 70-85°F (21-29°C)
- pH: 6.0-8.0
- Temperament: Fin nipper in small groups
- Diet: Omnivorous
Black skirt tetras are easy to find and easy to keep, but they come with a catch: they nip fins. Slow, long-finned tank mates like bettas, angelfish, or guppies will get harassed. The solution is simple: keep them in a larger group. Eight or more fish redirect the energy inward within the school rather than outward at your other stock.
In the right tank with the right companions, they’re dramatic and active. The flowing black fins against a planted background look excellent. Just don’t pair them with anything delicate.
5. Black Moor Goldfish
- Scientific Name: Carassius auratus
- Difficulty Level: Intermediate
- Adult Size: 6-8 inches (15-20 cm)
- Minimum Tank Size: 30 gallons (113 L) per fish
- Temperature: 60-72°F (15-22°C)
- pH: 7.0-8.0
- Temperament: Peaceful
- Diet: Omnivorous
Black moors are stunning. Velvety black, telescope eyes, flowing tail fins. They look like they belong in a painting. But here’s the reality: they’re fancy goldfish, which means cold water, massive bioload, and slow movement that makes them easy targets in mixed tanks.
Cold water is non-negotiable. Black moors do not go in tropical tanks. 72°F (22°C) is about the top of their range. They produce an enormous amount of waste for their size, so filtration needs to be rated higher than the tank size suggests. Plan on 30 gallons (113 L) per fish minimum, more if you want them to reach full size.
If you keep them in the right conditions, they can live 15 to 20 years. That’s a long-term relationship, not an impulse purchase.
6. Red-Tail Black Shark
- Scientific Name: Epalzeorhynchos bicolor
- Difficulty Level: Intermediate
- Adult Size: 4-6 inches (10-15 cm)
- Minimum Tank Size: 55 gallons (208 L)
- Temperature: 72-79°F (22-26°C)
- pH: 6.5-7.5
- Temperament: Territorial, especially toward own species
- Diet: Omnivorous
One per tank. That’s the rule. Red-tail black sharks are highly territorial toward their own species and similar-looking fish. They’ll chase and stress anything that invades their perceived territory, and as they mature that territory expands. Beautiful fish, velvety black with a brilliant red tail, but they need space and they need to be the only one of their kind in the tank.
A 55-gallon (208 L) is the minimum. In a 30-gallon (113 L), they stress your other fish constantly. Wild-caught specimens are now considered extinct in Thailand, so tank-bred stock is what you’ll find at reputable suppliers.
7. Black Ghost Knifefish
- Scientific Name: Apteronotus albifrons
- Difficulty Level: Advanced
- Adult Size: 18-20 inches (46-51 cm)
- Minimum Tank Size: 100 gallons (378 L)
- Temperature: 73-82°F (23-28°C)
- pH: 6.0-8.0
- Temperament: Peaceful toward large tank mates, predatory toward small fish
- Diet: Carnivore
The black ghost knifefish is one of the most remarkable freshwater fish in the hobby. It generates a weak electric field to navigate in the dark, detects prey through electroreception, and moves by undulating a single long fin rather than its body. It’s genuinely alien. I’ve kept one, and feeding time is an event. They learn to take food from your hand within weeks.
But they’re not beginner fish. Not even close. They need a mature, established tank over 100 gallons (378 L). They’re scaleless, which means they’re sensitive to medications and ich treatments. They’re nocturnal, so a daytime observer gets nothing. They eat small fish. And they live 10 to 15 years, growing to nearly 20 inches (51 cm).
Don’t buy a black ghost knifefish because it looked cool at the store. Buy one because you have the tank, the filtration, and the commitment. If you do, you’ll have one of the most interesting fish in freshwater.
8. Black Arowana
- Scientific Name: Osteoglossum ferreirai
- Difficulty Level: Expert
- Adult Size: 24-35 inches (61-89 cm)
- Minimum Tank Size: 250 gallons (946 L)
- Temperature: 75-84°F (24-29°C)
- pH: 4.0-6.5
- Temperament: Predatory surface fish
- Diet: Carnivore, primarily live and prepared meaty foods
This is expert-only, period. The black arowana is a surface predator from the Rio Negro in Brazil, found in soft, very acidic blackwater conditions. In the wild, it jumps to catch insects and small birds off overhanging branches. In captivity, it needs a massive custom setup, extremely soft and acidic water, and years of dedicated ownership.
Black arowanas sold as juveniles are often 3-4 inches (7.5-10 cm) and look manageable. They become 35-inch (89 cm) apex predators that eat anything that fits in their mouth. This fish defines the tank it lives in. There is no community with a black arowana. It is the tank.
AVOID IF
You have a tank under 55 gallons (208 L) and want anything on this list beyond tetras and mollies. You have slow-finned fish (bettas, fancy guppies, angelfish) and are considering black skirt tetras. You want a community tank and are eyeing the black ghost knifefish or arowana. You have a tropical setup at 78°F (26°C) and are considering a black moor goldfish. You’re a first-time fishkeeper and any store employee is recommending a black ghost knifefish or arowana as “interesting.”
Saltwater Black Fish
Saltwater options are limited but striking. These require established reef or fish-only systems. Not beginner territory.
Black Ocellaris Clownfish (Darwin Variant)
A black snowflake that resembles a traditional ocellaris with a misbar stripe in the middle
- Scientific Name: Amphiprion ocellaris (Darwin/black variant)
- Difficulty Level: Beginner to Intermediate (saltwater)
- Adult Size: 3 inches (7.5 cm)
- Minimum Tank Size: 20 gallons (75 L)
- Temperature: 75-82°F (24-28°C)
- pH: 8.1-8.4
- Reef Safe: Yes
- Tank Bred: Yes
The Darwin black clownfish is a naturally occurring black variant from Darwin, Australia. Unlike artificially colored fish, the black coloration is genetic and permanent. They behave identically to standard ocellaris clownfish: hardy, reef-safe, and easier to keep than most saltwater fish. Always buy tank-bred specimens.
Black Tang
- Scientific Name: Zebrasoma rostratum
- Difficulty Level: Advanced
- Adult Size: 9 inches (23 cm)
- Minimum Tank Size: 180 gallons (681 L)
- Temperature: 72-78°F (22-26°C)
- pH: 8.1-8.4
- Reef Safe: Yes
- Tank Bred: No
The black tang is one of the rarest tangs in the hobby. Solid black, reef-safe, and commanding in a large display tank. It commands the price to match: typically $400 to $800 or more depending on availability. Needs 180 gallons (681 L) minimum with lots of open swimming room. This is a centerpiece fish for a serious large-tank keeper, not a casual addition.
Banggai Cardinalfish
- Scientific Name: Pterapogon kauderni
- Difficulty Level: Beginner (saltwater)
- Adult Size: 3 inches (7.5 cm)
- Minimum Tank Size: 20 gallons (75 L)
- Temperature: 78-82°F (26-28°C)
- pH: 7.8-8.2
- Reef Safe: Yes
- Tank Bred: Yes
The Banggai cardinalfish isn’t solid black, but the bold black bar pattern against silver makes it one of the most graphically striking small saltwater fish available. It’s among the easiest saltwater fish to keep: hardy, reef-safe, and available tank-bred. Always buy tank-bred to avoid supporting wild collection from Banggai Island, where the wild population has been significantly reduced by the aquarium trade.
MARK’S PICK
For freshwater: the black phantom tetra. It’s underrated, genuinely interesting behaviorally, and works in most community tanks. If you want something more dramatic and you have the setup for it, the black ghost knifefish is one of the most remarkable fish in the hobby. Just go in with eyes open about what it actually needs. For saltwater: the Darwin black clownfish is the accessible pick. If you’re running a large reef system and have the budget, the black tang is as good as it gets.
What People Get Wrong About Black Fish
The biggest mistake I see: people buying black fish purely for the aesthetic without checking the care level. The black ghost knifefish is sold at chain stores in small tanks labeled “peaceful community fish.” It is not. It grows to 20 inches (51 cm), needs a 100-gallon (378 L) mature setup, and eats smaller tank mates. That store label is wrong.
Second most common mistake: putting black moor goldfish in tropical tanks. They need 60-72°F (15-22°C) water. At 78°F (26°C), their immune system is compromised and their lifespan shortens dramatically. Goldfish and tropical fish don’t share tanks. Period.
Third: assuming all black tetras are the same. Black skirt tetras nip fins. Black neon tetras don’t. Black phantom tetras display but don’t nip. They’re very different fish in terms of community compatibility.
Should You Get a Black Fish?
Good fit if:
- You want high contrast in a planted tank without a species that requires expert-level care
- You’re building a monochromatic or dark-themed display tank
- You want a schooling fish with visual impact (black neon or phantom tetra)
- You have a 100-gallon (378 L)+ mature setup and want a long-term showpiece (black ghost knifefish)
- You’re an experienced saltwater keeper with a large display tank (black tang)
Avoid if:
- You have a small tank under 30 gallons (113 L) and want anything larger than a tetra
- You’re pairing with slow-finned fish like fancy guppies, bettas, or angelfish and want black skirt tetras
- You’re new to fishkeeping and a sales employee is steering you toward a black ghost knifefish or arowana
- You’re running a tropical tank and want black moor goldfish
Where to Buy
For black mollies, black neon tetras, and black skirt tetras, most local fish stores carry them regularly. For black phantom tetras, black ghost knifefish, and Darwin black clownfish, online specialty retailers are more reliable for healthy, quality stock.
Flip Aquatics is one of the best sources for quality freshwater species, with healthy stock and excellent support. Dan’s Fish is another strong option for specialty species. Both ship directly to your door.
FAQ
What is the easiest black freshwater fish to keep?
The black molly is the most beginner-friendly option. It’s hardy, adaptable, and genuinely black. Black neon tetras and black phantom tetras are close behind for ease of care in a community setting.
Is the black ghost knifefish good for beginners?
No. It’s frequently sold as a community fish, but it requires a 100-gallon (378 L) mature tank, is sensitive to medications, grows to 20 inches (51 cm), and eats small fish. It’s an advanced-level species regardless of how it’s marketed at chain stores.
Can black moor goldfish live with tropical fish?
No. Black moors need cold water between 60-72°F (15-22°C). Tropical tanks run at 76-80°F (24-27°C), which causes chronic stress and shortens their lifespan significantly. They need a goldfish-only or cold-water setup.
Do black skirt tetras really nip fins?
Yes, in small groups. A school of 8 or more reduces nipping substantially because the energy stays within the school. Pair them with short-finned, fast-moving tank mates and avoid bettas, fancy guppies, and angelfish.
What is the difference between a black neon tetra and a black phantom tetra?
Both are peaceful schoolers, but they’re different species with different appearances. The black neon tetra has a horizontal black band with a white line above it. The black phantom tetra has a rounder body with a prominent black spot behind the gill and darker overall coloration. Black phantom males display against each other with spread fins, which the black neon does not do.
How large does a black arowana get?
Black arowanas regularly reach 24-35 inches (61-89 cm) in captivity. They need a minimum 250-gallon (946 L) tank as adults and extremely soft, acidic water to match their Rio Negro natural habitat. This is an expert-only fish with a decades-long ownership commitment.
Closing Thoughts
Black fish are some of the most visually impactful species in the hobby, but the range in difficulty is wider than almost any other color-themed category. A black molly is a beginner fish. A black arowana is an expert commitment. Don’t let the color drive the purchase. Let the tank size, the experience level, and the long-term plan drive it.
If you’re just starting out, black neon tetras or black phantom tetras give you striking dark fish in a manageable package. If you have the infrastructure for something more serious, the black ghost knifefish is genuinely one of the most fascinating fish in freshwater. Either way, buy from quality sources and buy fish that fit the tank you actually have, not the tank you’re planning to get someday.
Ready to add one to your tank? Check out Flip Aquatics for healthy, quality freshwater stock, or Dan’s Fish for specialty species selection.
- About the Author
- Latest Posts
I’m Mark Valderrama, founder of Aquarium Store Depot and a fishkeeper with over 25 years of hands-on experience. I started in the hobby at age 11, worked at local fish stores, and have kept freshwater tanks, ponds, and reef tanks ever since. I’ve been featured in two best-selling aquarium books on Amazon and built this site to share practical, experience-based fish keeping knowledge.
Leave a Reply