Meet the molly – a docile pet fish

The molly is a tropical fish who likes a little bit of salt in their water. Generally said to be easygoing, easy to care for and a good option for the beginner fishkeeper, there are a few things about molly fish you need to know before deciding on getting your own.

A place called home

While said to be brackish fish, you can find the molly living in the wild both in freshwater areas as well as completely saltwater. They spend their days foraging for food, and in the wild they feed on algae, other forms of plant life, and as they are omnivores, their diet is supplemented by live foods. If you want to keep mollies as pets, you will need to keep in mind that they are tropical fish, and therefore you will need to invest in an aquarium heater. The temperature of the water should be between 22 and 28°C. The pH levels of the water should be between seven and eight.


Mollies are mostly peaceful, but you will have to do some research if you want to keep them with other species of fish, particularly species with long and flowing fins. This is because the molly tends to nip on other fish’s fins, removing some of the slime coat that protects the other fish. This causes stress that will affect the immune system of the other fish, and potentially lethal infections might develop. On the other hand, combining the docile molly with large, aggressive species might lead to your mollies being bullied. As tropical fish they can obviously not be placed with coldwater species, and also take care with fish that are much smaller than them – the omnivorous nature might come through, leading to your mollies munching on their roommates. They will also eat their own as well as other fish’s fry, so rather remove baby fish from the tank if you are planning to keep them.

Mollies like to live in small groups, so one male along with a few females will be a good combination, as well as all females if you don’t want to deal with them having babies on a regular basis. Keeping only males might result in fighting. Mollies are not schooling fish, and in their smaller groups they form a strict hierarchy, with the male with the biggest fins and strongest colours usually being the leader.

Babies by the dozens

Mollies make babies. A lot. If you have males and females, chances are that the female will be pregnant most of the time. As the male will constantly attempt to mate, it’s a good idea to keep a ratio of about three females to every male to prevent the female becoming stressed from the constant mating attempts. Mollies are livebearers, meaning that they don’t lay eggs but give live birth instead. If the conditions in the tank are right, a molly can give birth every 30 days, with the gestation period being around four weeks. They can give birth to anything from two to 60 fry at a time! The number of fry depends on the size, age and health of your molly.

It might be disturbing to see the mother molly feast on her babies, but this is quite normal and is thought to keep the population under control, considering the rate at which they breed. If you want to prevent this, you can remove a pregnant molly (who will develop a big belly) from the other fish to a separate tank. Make sure the water conditions in the new tank are exactly the same as in the previous tank. Once she has given birth to the fry, you can once again remove her and place her back in the previous tank.

Mollie fry are born swimming and are able to eat on their own right from the start. It’s a good idea to provide live plants or algae, and adult flakes that you ground up into a powder. The fry can be moved to the main tank as soon as they are too big to fit into the mouths of the adults in the tank.

Did you know?

You can tell the gender of your molly by looking at the anal fin. In males it tends to be much smaller and more elongated