- Common name
- Amazon molly
- Scientific name
- Poecilia formosa
- Category
- Freshwater fish
- Group
- Livebearers and mollies
- Environment
- Freshwater and brackish habitats
- Origin
- Lower Nueces and lower Rio Grande drainages in the United States south through Gulf-slope drainages to Veracruz, Mexico
- Care level
- Intermediate
- Adult size
- Up to 9.6 cm total length; about 5.5 cm is more common
- Expected lifespan
- Plan for about 3–5 years; donor-species interactions, mineral stability and repeated pregnancy can affect individual survival.
- Minimum housing
- At least 100 litres for a group, with additional room for the compatible sperm-donor species used in reproduction
- Temperature
- Unknown — reported as a subtropical fresh-to-brackish species
- pH
- Unknown — no dependable species-specific aquarium range found
- Hardness / minerals
- Unknown — naturally occurs in fresh and brackish waters; maintain stable mineral-rich water appropriate to documented stock origin
- Salinity
- Freshwater to brackish, depending on locality and stock history; do not change salinity abruptly
- Lighting
- Normal aquarium lighting with plant or wood cover
- Placement / zone
- All levels, especially middle and upper water
- Filtration
- Use mature biological filtration with protected intakes and moderate circulation. Size solids capture for an active livebearer group, plant-rich feeding and any donor-species fish required by a deliberate breeding plan.
- Aeration
- Maintain strong surface exchange and oxygenated warm water. Increase aeration during pregnancy, high temperature, crowding or medication.
- Maintenance
- Perform regular mineral-matched water changes, remove excess food, control fry numbers, monitor females for body condition and birth complications, and record the identity of all donor stock.
Identity and search names
Use only for verified Poecilia formosa. Trade stock without provenance may be another Poecilia species or hybrid.
Search names: Amazon molly, Unisexual molly
Environment and housing
Open swimming lanes, planted or structured refuge, and strong biological filtration.
Social structure: Maintain multiple females with compatible donor males only when a deliberate breeding plan exists. Monitor interspecific harassment.
Feeding and nutrition
Feeding ecology: Omnivore; algae, plant material, small invertebrates and quality prepared foods
Feeding routine: One or two measured feeds daily; adapt to body condition and species ecology
Breeding, reproduction or spread
Gynogenetic livebearer. Females require mating with males of compatible related species, but offspring are normally genetic copies of the maternal line.
Detailed care and app-ready planning
- Identity scope
- Use only for verified Poecilia formosa. Trade stock without provenance may be another Poecilia species or hybrid.
- Adult size and space
- Plan for females up to 9.6 cm TL and the additional donor-species fish needed for reproduction.
- Social structure
- Maintain multiple females with compatible donor males only when a deliberate breeding plan exists. Monitor interspecific harassment.
- Swimming zone or placement
- Uses middle and upper water and grazes surfaces.
- Feeding ecology
- Omnivorous grazer taking algae, detritus, plant material and small invertebrates.
- Feeding plan
- Provide plant-rich staple food with small protein feeds; prevent dominant livebearers from monopolising food.
- Water stability
- Keep mineral content, temperature and salinity stable. Acclimate slowly between fresh and brackish conditions.
- Habitat structure
- Open swimming lanes, planted or structured refuge, and strong biological filtration.
- Compatibility plan
- Choose species with matching water needs. Do not add donor males casually; identify the species and monitor aggression.
- Breeding or reproduction plan
- Maintain verified donor males, record parent stock and control fry numbers before breeding.
- Quarantine
- Quarantine all Poecilia stock and screen for wasting, external parasites and abnormal swimming.
- Welfare checks
- Check body condition, spine shape, respiration, birthing complications, harassment and fry overpopulation.
- Biosecurity and release
- Never release livebearers or aquarium water. Poecilia can establish invasive populations; check Australian and state rules.
- Main risk
- Misidentification and uncontrolled reproduction involving an unsuitable donor species.
- Adult projected load
- Project load from the full female group, compatible donor males and repeated fry production. Uncontrolled reproduction can turn a moderate adult load into chronic crowding very quickly.
- Filtration
- Use mature biological filtration with protected intakes and moderate circulation. Size solids capture for an active livebearer group, plant-rich feeding and any donor-species fish required by a deliberate breeding plan.
- Aeration
- Maintain strong surface exchange and oxygenated warm water. Increase aeration during pregnancy, high temperature, crowding or medication.
- Maintenance
- Perform regular mineral-matched water changes, remove excess food, control fry numbers, monitor females for body condition and birth complications, and record the identity of all donor stock.
- Overridable warnings
- Non-overridable: use verified Poecilia formosa identity, compatible donor stock, stable minerals and a fry-capacity plan. Breeding or salinity methods may vary only when lineage records, welfare and lawful containment are maintained.
- Identity
- Poecilia formosa is a valid unisexual species. It must not be confused with an ordinary female-only group of another molly.
- Environment
- Use stable, well-filtered mineral-rich water and open swimming space with refuge. Match salinity to known stock history rather than assuming every population is brackish.
- Feeding
- Offer algae-based prepared foods, vegetable matter and small animal foods. Avoid a high-fat diet.
- Breeding
- Gynogenetic livebearer. Females require mating with males of compatible related species, but offspring are normally genetic copies of the maternal line.
- Adult size and space
- Plan for females up to 9.6 cm TL and the additional donor-species fish needed for reproduction.
- Biosecurity and release
- Never release livebearers or aquarium water. Poecilia can establish invasive populations; check Australian and state rules.
- Welfare Risk
- Chronic harassment, mineral instability and overcrowding are the main welfare risks.
Compatibility, welfare and risk
Compatibility: Peaceful livebearers and other fish sharing the same mineral and salinity requirements
Welfare: Chronic harassment, mineral instability and overcrowding are the main welfare risks.
Main warning: All-female reproduction still requires sperm from a compatible related male to trigger embryonic development; ordinary sex ratios do not apply.
Biosecurity and release
Never release livebearers or aquarium water. Poecilia can establish invasive populations; check Australian and state rules.