Care guide · Freshwater · fish

Sailfin molly

Poecilia latipinna

Sailfin mollies in the wild. Photo: Jacob Weston, CC BY 4.0. Photo: Jacob Weston · Source · CC BY 4.0none; original ratio retained

The sailfin molly (Poecilia latipinna) is a livebearing toothcarp native to the southeastern United States and Mexico. Adult males are best recognised by their large, sail-shaped dorsal fin. The species can reach about 12.5 cm standard length and the specialist profile gives a tank footprint of 76 × 38 cm (about 87 litres at 30 cm water depth). Sailfin mollies can live in freshwater, but need hard, mineral-rich, alkaline conditions; added salt is not routinely required. They eat substantial algae and plant material and may damage soft aquarium plants. Keep several females per male. Do not house them with other molly species if you want to avoid crosses: P. latipinna and P. sphenops can readily hybridise.

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At a glance

Temperature: 21–26 °C
pH: 7.0–8.5
GH: 15–35 °dGH
Aquarium length: At least 76 cm
Minimum aquarium volume: At least 87 L
Adult size: Up to 12.5 cm
Group size: At least 3 individuals
Temperament: Peaceful

About this species

Poecilia latipinna belongs to the family Poeciliidae and order Cyprinodontiformes. Eschmeyer’s Catalog of Fishes accepts Poecilia latipinna (Lesueur, 1821). Adult males develop a large sail-like dorsal fin; females are generally larger but have a smaller dorsal fin. The species may reach about 12.5 cm standard length, excluding the tail. FishBase reports up to 15 cm total length in males, which is a different measurement. Dark rectangular marks in the dorsal fin help distinguish it from P. velifera, but selectively bred colour strains and hybrids occur in trade. A retail colour name alone therefore cannot confirm species identity.

Natural habitat

The native range runs from North Carolina in the United States south to Veracruz, Mexico, according to the Catalog of Fishes. It inhabits warm, often vegetated coastal streams, ponds, ditches, swamps and quiet backwaters; brackish canals also occur in its range. Introduced populations have been reported in many countries, with adverse ecological effects in some places. Never release aquarium animals or plants into outdoor waters. Occurrence in brackish or coastal water does not mean salt is needed in a freshwater aquarium.

Aquarium and layout

Provide open swimming space with dense planting around the edges. The specialist source gives a 76 × 38 cm footprint and about 87 litres at 76 × 38 × 30 cm. This is a source-based guideline, not a universal stocking guarantee. Use a mature filter and keep water quality stable. Soft plants may be eaten or damaged; choose robust species and allow some algae to grow on suitable surfaces. In mixed-sex groups, keep at least two females per male to spread persistent courtship. Males may become aggressive toward each other, especially during breeding activity.

Water conditions

Seriously Fish gives 21–26 °C, pH 7.0–8.5 and GH 15–35 °dGH. FishBase reports a broader temperature band and records the species from fresh, brackish and marine waters; for aquarium care we follow the narrower specialist range. The fish needs hard, alkaline water and may weaken quickly in soft, acidic conditions. Calcium and magnesium matter more than routine salt addition: the specialist source says salt is not necessary. Measure your source water and change chemistry gradually.

Behaviour and group size

Sailfin mollies are generally suitable for hard-water communities, but adults may pick on smaller tankmates. Males may fight one another, particularly when females are present. Choose tankmates that tolerate hard, alkaline water and avoid very small, slow fish. P. latipinna readily crosses with P. sphenops; keep one molly species per aquarium if you want species-true offspring. Matching water values alone do not establish safe compatibility. The species is not universally plant-safe because soft leaves may be damaged.

Feeding

The natural diet consists largely of algae and other plant material, although small animal foods are also eaten. Use a complete tropical food as a practical staple and offer vegetable- or algae-rich foods regularly. An existing algae wafer can be used as a supplement, but it does not replace a varied complete diet. For adult males, provide enough plant matter; the specialist source warns that too little green food may impair dorsal-fin development. Feed modest portions and remove leftovers.

Breeding

The sailfin molly is livebearing. Seriously Fish recommends a trio of one male and two females because males may court persistently. FishBase and Seriously Fish differ on gestation and brood size, so this guide gives no exact duration or guaranteed number of fry. Dense plants provide cover, but adults and other fish may eat young. Plan for offspring in advance, and avoid mixing molly species if maintaining species identity matters.