Molly fish are easy to breed in a home aquarium and are often already pregnant when purchased at a pet store. They are peaceful fish that live well in a community.
Mollies breed using internal fertilization. The male molly inseminates the eggs while they are inside the female. She carries the eggs inside her until the fry, or newborn fish, are ready to be released.
The gestation period of a molly fish is around 60 days. Female mollies can store sperm for months and may fertilize eggs as often as every 30 days, even when no male is present in the tank. Mollies may release 10 to 60 live fish at a time.
To eliminate the possibility of the fry being eaten by larger fish in the tank, place the pregnant molly into a breeder net just before she is about to give birth. Once she releases the fry, remove her from the breeder net and allow the fry to remain until they are larger.