Shortfin molly
Poecilia sphenops
Requires relatively hard water; do not automatically add salt to a freshwater community tank. An active livebearing fish. Plan space for offspring and prevent persistent harassment of females.
At a glance
- Scientific name
- Poecilia sphenops
- Dutch name
- Molly
- Water temperature
- 21–28 °C
- pH
- 7–8.5
- Adult length, up to approximately
- 8 cm SL
- Experience
- Basic knowledge
- General hardness (GH)
- 15–30 °dGH
- Starting footprint
- 90 × 30 cm
- Swimming or living zone
- Several water levels
- Flow
- Moderate, with sheltered areas
This is a documented adult size, not a measured average. SL means body length excluding the tail fin. Sex, origin and cultivated form can affect size.
Care guidance; origin and captive breeding can change requirements. Some ranges are deliberately narrower than natural extremes in the source. Adjust water gradually and keep ammonia and nitrite at zero.
Tank sizes are editorial starting points for adults, not guarantees for a complete stocking plan. Group size, tank height, swimming length and territories may require a larger aquarium.
Origin
Tropical Americas — Mexico / Venezuela
Habitat & setup
Vegetated freshwater habitats; provide plants and quiet refuges.
Diet
Varied complete fish food with a plant component and small animal-based foods.
Behaviour & grouping
Group; more females than males, or a carefully chosen single-sex group.
Living with other animals
Peaceful hard-water fish of suitable size. Avoid species requiring soft acidic water; check hybridisation risks.
Reproduction
Livebearing; rapid population growth is possible. Plan space and responsible rehoming.
A suitable cover helps prevent escape and jumping. Protect intakes for small animals. Do not use copper-based fish medication with invertebrates.
Sources & image credits
Data compiled on: 2026-09-27. Species sources support identity and care; group sources give general starting points. Practical recommendations are an editorial synthesis.
Photo: Poecilia_sphenops,_Florida,_US_imported_from_iNaturalist_photo_487744119.jpeg — (c) James-LaFontaine, some rights reserved (CC BY). CC BY 4.0.