Shortfin Molly
Poecilia sphenops
The Shortfin Molly (Poecilia sphenops) is a semi-aggressive fish that's easy to keep. Give it a tank of at least 120 litres (32 US gallons), water held at 72-82°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
Americas / Africa (varies)
- Africa
- South America
- Central America & Mexico
Regional colours match the stocking calculator's origin map.
Shortfin Molly Tank Setup
A tank of at least 120 litres (32 US gallons) at 72-82°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.
What Do Shortfin 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.
Shortfin Molly Tank Mates
Keep in groups of at least 6. The Shortfin 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 Shortfin 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.
Shortfin Molly - frequently asked questions
What size tank do Shortfin Mollies need?
Shortfin Mollies need a tank of at least 120 litres (32 US gallons). A bigger tank is always easier to keep stable, and gives them more room to settle in and behave naturally.
How many Shortfin Mollies should I keep together?
Keep a group of at least 6. Shortfin Mollies are a shoaling species and become stressed, lose their colour, or hide when kept singly or in pairs.
What water parameters do Shortfin Mollies need?
Keep them at 72-82°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 Shortfin Mollies eat?
Shortfin 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 Shortfin Mollies good for beginners?
Yes - Shortfin 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 Shortfin Mollies
- Buying fewer than 6 - Shortfin Mollys need a proper school to feel secure; isolated individuals hide, fail to colour up, or become stressed.
- Underestimating tank size - the minimum footprint is 120 litres (32 US gallons); impulse buying into a smaller tank leads to stress and shortened lifespan.
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 Shortfin 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
