Mollies are common freshwater aquarium fish. They look a lot like a cross between a tetra and a fancy goldfish. There are two main varieties of mollies, short-fin and sailfin. Sailfin mollies are much larger with longer fins than their short-fin counterparts. They give birth to live young, and even the most novice of fish keepers will probably produce offspring. If the young are not removed immediately, they will become snacks. To avoid breeding, you should keep only males or only females. Males and females can be differentiated by the shape of their anal fin. Males have a anal fin that points backwards. Females’ anal fin looks just like the rest of their other fins.
More than one molly can be kept in a tank together, however, they have been known to nip the fins of others in their tank. It is recommended that only one male molly be kept in a tank since males will fight with each other to establish a dominant alpha fish. With this type of fish, you should stick to the 1 gallon of water per 1″ of fish. Since mollies usually grow up to 2″, a 10 gal tank should have no more than 4-5 fish. When thinking about how many fish you want in your tank, it is always better to err on the side of too few. Mollies can be fed a combination of flake food (main base food) with other occasional supplements, such as brine shrimp or blood worms.