Black Molly
Poecilia sphenops
The Black Molly (Poecilia sphenops) is a semi-aggressive fish that's easy to keep. Give it a tank of at least 90 litres (24 US gallons), water held at 70-82°F, and a pH of 6.8-8.2. Always keep a group of at least 6 - they feel safest in numbers.
Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.
Natural distribution
Captive-bred; wild mollies range fresh and brackish waters of Mexico and the southern USA.
- Africa
- South America
- Central America & Mexico
Regional colours match the stocking calculator's origin map.
Black Molly Tank Setup
A tank of at least 90 litres (24 US gallons) at 70-82°F and pH 6.8-8.2 suits them well. Livebearers breed quickly, so plan for the fry and keep an eye on your male-to-female ratio. Always keep a group of at least 6 of their own kind - kept alone or in pairs they tend to turn shy, nippy, or wash out in colour. They reach about 12 cm as adults, so don't be misled by the small juveniles sold in stores.
What Do Black Mollies Eat?
They're not fussy eaters - feed a varied diet, rotating good-quality dry, frozen, and gel foods rather than the same thing every day, and match the food size to their mouths.
Black Molly Tank Mates
Keep in groups of at least 6. The Black Molly is semi-aggressive, which is the first thing to weigh up when you choose tank mates. It's a shoaling fish, so settle a group of 6 or more of its own kind before adding anything else - a stressed, lonely fish is far more likely to nip or hide. Before you buy, run your full stocking list through our stocking calculator. It weighs temperament, adult size, and water needs together, which a single species page can't do on its own.
Are Black Mollies Good for Beginners?
Often recommended to beginners, but only after the tank is cycled and you can keep a proper school - not three fish in a new setup.
Black Molly - frequently asked questions
What size tank do Black Mollies need?
Black Mollies need a tank of at least 90 litres (24 US gallons). A bigger tank is always easier to keep stable, and gives them more room to settle in and behave naturally.
How many Black Mollies should I keep together?
Keep a group of at least 6. Black Mollies are a shoaling species and become stressed, lose their colour, or hide when kept singly or in pairs.
What water parameters do Black Mollies need?
Keep them at 70-82°F with a pH of 6.8-8.2, steady rather than chased to an exact figure. In a cycled tank, ammonia and nitrite should both read 0 ppm, with nitrate kept low through regular water changes.
What do Black Mollies eat?
Black Mollies are omnivores and aren't fussy eaters. Feed a varied mix of good-quality dry, frozen, and gel foods, and match the food size to their mouths. Feed small amounts once or twice a day, and remove anything they don't eat.
Are Black Mollies good for beginners?
Yes - Black Mollies are a good beginner choice once the tank is fully cycled and you can keep a proper group. They are hardy but still need stable water and a school to feel secure.
Common mistakes with Black Mollies
- Buying fewer than 6 - Black Mollys need a proper school to feel secure; isolated individuals hide, fail to colour up, or become stressed.
Guides that pair with this fish
- Molly care guide - Salinity debates framed calmly.
- Molly tank mates - Peaceful brackish-tolerant mixes.
- Guppy care guide - Overlapping livebearer feeding rhythm.
Building a community? Run the full list through the stocking calculator before you add anything else.
Great tank mates
Chosen from temperament, overlapping temperature/pH bands, plausible minimum tank footprints, and size versus yours in App-aquatic data. Hobby nuance always wins - verify stocking and temperament before purchasing.
Fish to avoid mixing with Black Mollies
These well-known species are commonly sold alongside this fish but are not recommended tank mates - verify before purchasing.
- OscarPredator - Oscar will eat or injure smaller tank mates
- Pea PufferPredator - Pea Puffer will eat or injure smaller tank mates
- Betta (Male)Predator - Betta (Male) will eat or injure smaller tank mates
