Mollies are active, hardy livebearers native to the Americas. They are famous for their ability to adapt to fresh, brackish, and even full marine water. They are voracious eaters (including algae) and produce a high bioload for their size. Note: 'Molly' covers several species; the Short-finned (*P. sphenops*) and the much larger Sailfin (*P. latipinna* and *P. velifera*).
At a Glance
Tank Requirements
Water Parameters
Temperament & Compatibility
Available Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Short-Finned (Standard)
The standard *Poecilia sphenops*. Stocky but agile. Males may harass females constantly; a ratio of 1 male to 3 females is recommended to disperse stress.
Differs in 3 traits from base species
Also known as: Black Molly, Dalmatian Molly, Gold Molly, P. sphenops
Sailfin Molly
Significantly larger than standard mollies with a spectacular dorsal fin. Requires more swimming space and stable vegetable matter in their diet.
Differs in 4 traits from base species
Also known as: P. latipinna, P. velifera, Green Sailfin, Giant Sailfin, Yucatan Molly
Balloon Molly
A man-made morph with a deformed spine resulting in a round, balloon-like body. They are prone to swim bladder issues and digestive problems. They cannot swim as strongly as standard mollies.
Differs in 4 traits from base species
Also known as: Potbelly Molly
Molly (Sailfin/Black/Dalmatian) Care Summary
The Molly (Sailfin/Black/Dalmatian), scientifically known as Poecilia sphenops, belongs to the Livebearers family group. Adults reach a maximum size of approximately 10 cm and have a fusiform body shape with a fast growth rate. Classified as mostly peaceful, this species primarily occupies the surface and mid-level zones of the aquarium and produces a high level of biological waste.
To thrive, the Molly (Sailfin/Black/Dalmatian) requires a brackish tolerant aquarium with a minimum volume of 75 litres and a tank length of at least 60 cm. Water temperature should be maintained between 24°C and 28°C, with a pH range of 7.5–8.5 and a general hardness of 12–30 dGH. A moderate water flow is preferred. To replicate their natural habitat, the tank should include plants - densely covered and established algae (otocinclus).
This species should be kept in groups of at least 3 to reduce stress and encourage natural behaviour. This species is available in 3 varieties: Short-Finned (Standard), Sailfin Molly, and Balloon Molly. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Similar Species
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