The Black Arowana (Osteoglossum ferreirai) is one of the most striking fish a large-tank keeper can own. It’s a close cousin of the more common Silver Arowana, with the same long, sleek body, big upturned mouth, and graceful way of patrolling the top of the tank. But it’s rarer, more expensive, and a little more delicate, especially when young.
If you’re thinking about adding one to your home, here’s what it takes to keep a Black Arowana healthy for the long haul.
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Quick Facts
| Scientific name | Osteoglossum ferreirai |
| Origin | Rio Negro basin, South America |
| Adult size | Around 2½ to 3 feet |
| Minimum tank | 250+ gallons for an adult |
| Temperature | 77–86°F (25–30°C) |
| pH | Slightly acidic to neutral, about 5.5–7.0 |
| Diet | Carnivore, feeds mainly at the surface |
| Lifespan | 10–15+ years with good care |
Black Arowana vs. Silver Arowana
Young Black Arowanas are dark, nearly black, with a bright yellow-orange stripe along the body. As they grow, they turn a silvery blue-gray, and the fins develop dark edges with hints of yellow or red. Adults look similar to Silver Arowanas, so the juveniles are what most people picture when they hear the name.
Black Arowanas come from the Rio Negro, a soft, tea-colored “blackwater” river. That’s why they prefer softer, more acidic water than the Silver, and why young fish are more sensitive to poor water quality and sudden changes. For a comparison, see my Silver Arowana care guide.
Tank Size and Setup
A juvenile may be only a few inches long in the store, but it will grow quickly. Plan for the adult. A 250-gallon aquarium or larger is the realistic minimum, and the tank should be long and wide so the fish can turn around comfortably. Width matters as much as length for a fish this long.
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- A heavy, tight-fitting lid: Arowanas are powerful jumpers. A secure lid with no gaps is not optional.
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- Open swimming space: They spend most of their time near the surface. Keep the upper part of the tank clear and put decor lower down.
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- Substrate: Sand or a bare bottom both work. A bare bottom is easier to keep clean with such a messy eater.
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- Driftwood: Pieces of Malaysian driftwood or Mopani driftwood fit the Black Arowana’s natural habitat. The tannins they release gently soften the water and tint it, which suits this blackwater species. Indian almond leaves do the same.
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- Lighting: Moderate lighting on a timer works best. Sudden lights-on in a dark room can startle them into jumping, so it helps to turn on a room light first.
Water Conditions
Keep the temperature between 77°F and 86°F with a heater sized for a large tank, and check it with a separate thermometer. On a big tank, two heaters placed apart give more even heat and a backup if one fails.
Black Arowanas do best in slightly acidic to neutral water, roughly pH 5.5 to 7.0. Aim for stability rather than a perfect number, and make any changes gradually. Ammonia and nitrite should always be zero and nitrate kept low. Test regularly with a freshwater test kit.
Filtration and Water Changes
A large predator produces a lot of waste, so filtration needs to be strong. One or more large canister filters or a sump system rated well above your tank volume is a good approach. Keep the surface moving for oxygen. An air pump and air stones help, especially at the warmer end of the temperature range.
Change about 25–30% of the water every week. On a tank this size, a Python water changer saves a lot of bucket-hauling. Treat the new water with a conditioner such as Seachem Prime, which treats large volumes economically, and match the temperature closely.
Feeding Your Black Arowana
Black Arowanas are carnivores, and that upturned mouth tells you where they like to eat: at the surface. In the wild they snatch insects, shrimp, and small fish from the top of the water. Foods that float work best.
Good choices include:
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- Floating arowana sticks or pellets as the staple
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- Crickets and other insects
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- Krill and shrimp
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- Live or frozen blackworms for juveniles
Feed juveniles two or three small meals a day and adults once or twice a day. Don’t overfeed. Uneaten food fouls the water quickly in a warm tank.
Be careful with live feeder fish. They’re cheap, but they’re one of the most common ways parasites and disease get into an arowana tank, and they’re often low in nutrition. If you use them, quarantine and gut-load them first, or skip them entirely in favor of insects and prepared foods.
Tank Mates
Anything small enough to fit in a Black Arowana’s mouth will eventually be eaten. Good tank mates are large, peaceful-to-semi-aggressive fish that stay mostly in the middle and lower levels of the tank, such as large plecos, silver dollars, and larger peaceful cichlids or catfish. A Black Ghost Knife Fish can also work in a very large tank.
Avoid fin-nippers and other surface-dwelling predators that will compete for the same space. Most keepers house only one arowana per tank, because they can be aggressive toward their own kind.
Health Problems to Watch For
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- Jumping injuries: The most common cause of arowana loss. Keep that lid secure.
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- Drop eye: One or both eyes start pointing downward. It’s often linked to the fish constantly looking down at food or tank mates. Feeding at the surface and keeping the bottom uninteresting may help.
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- Gill curl: The edges of the gill covers curl outward, often a sign of poor water quality or low oxygen.
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- Fin rot and fungus: Usually tied to water quality. Fix the water first.
Watch for loss of appetite, clamped fins, cloudy eyes, or unusual behavior. If something looks wrong, test the water before reaching for medication.
Is a Black Arowana Right for You?
A Black Arowana is a long-term commitment. You need a very large tank, strong filtration, a secure lid, and the dedication to keep up with weekly water changes for 10 to 15 years or more. If you can provide that, few fish are more impressive to watch as they glide along the surface of the tank.
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