Balloon Molly

Looks how to spot one

Fish body

The balloon molly has a distinctive rounded, balloon-like belly and an arched back, which come from a genetic spinal curvature. It also has a large, lyre-shaped tail fin and a prominent dorsal fin. The body is otherwise similar to the sailfin molly, but the rounded shape is the defining feature.23

Personality what they are like

Balloon mollies are generally peaceful and do well in community tanks with other calm fish of similar size. Males can be a bit quarrelsome with each other, especially when courting females, and they may chase their own young. They are lively and active swimmers.231

Daily activity how busy a day looks

They need a tank of at least 20 to 30 gallons (about 75 to 115 litres) with plenty of swimming space. Dense planting with hardy plants like Java fern, Vallisneria, and Anubias provides hiding spots and mimics their natural habitat. They are active during the day and appreciate open areas for swimming.246

Grooming and care the hands-on bits

Care is straightforward for beginners. They need a good filtration system because they produce a fair amount of waste. Regular water changes are important, and the replacement water should be warmed to the tank temperature to avoid shocking the fish. They are sensitive to soft, acidic water, so keep the water hard and alkaline. Adding a little aquarium salt is optional but can help, as they tolerate brackish conditions.213

Home where they are happiest

In the wild, sailfin mollies live in warm, slow-moving streams, ponds, and coastal brackish waters with lots of vegetation. In the aquarium, they need a tank of at least 20 gallons (75 litres) with a length of at least 60 cm. Water temperature should be 22-28°C, pH 7.0-8.5, and hardness moderate to high. They can be kept in freshwater or brackish water, but soft and acidic water is harmful. Dense planting is recommended, though they may nibble soft-leaved plants.143

Food basics what goes in the bowl

Balloon mollies are omnivores, but they need plenty of plant matter. In the wild they eat algae, diatoms, and insect larvae. In the aquarium, offer a good quality algae-based flake or pellet food, plus blanched vegetables like spinach or lettuce. You can also give them live or frozen foods such as brine shrimp, bloodworms, or daphnia as occasional treats, but avoid too much animal protein, especially for young fish.213

Company who they like around

They are social and should be kept in groups of at least five, with more females than males to reduce harassment. They are peaceful with other community fish, but males can be aggressive to each other. They may eat their own fry, so provide dense plants or a separate breeding tank if you want to raise young. They are not venomous or illegal to keep.312

The story where it all began

The balloon molly is a selectively bred variety of the sailfin molly, Poecilia latipinna. It was developed in captivity for its unusual rounded body shape, which comes from a genetic spinal curvature. This variety is popular in the aquarium trade because of its distinctive appearance and easy care. Unlike the wild sailfin molly, which has a more streamlined body, the balloon molly has a shortened, arched spine that gives it a balloon-like belly. This variety is bred in fish farms, mainly in the Far East and Eastern Europe, and is now common in pet shops worldwide.231