Can Guppies And Mollies Crossbreed?

Mollies and guppies are active fishes with unique personalities and plenty of interesting behaviours. They belong to the same family known as Poeciliidae as well as the same genus called Poecilia. However, a lot of people who operates aquarium have a general question and the question is if guppies and mollies can crossbreed.

Technically, the answer is YES. Guppies and mollies can crossbreed largely because they belong to the same family and genus.  However, they naturally don’t interbreed with each other. This is because the fry from this crossbreed tends to die right after birth or even during birth. Only a few of them make it to the adult stage and they are usually sterile even if they do survive.

Guppies And Mollies Crossbreed

Guppies Breeding And Reproduction

Guppies are generally live bearers which translates to the fact that they give birth to their babies (fry) alive. Unlike other fishes like goldfish that lay eggs, guppies are quite different because their fry comes alive. Guppies breed rapidly and freely, meaning you can have the number of your pet guppies multiplied in a relatively short period.

Like other popular members of the Poeciliidae family, male guppies have a highly modified tubular anal fin known as gonopodium that can be found directly behind the ventral fin. The gonopodium is the channel in male where loads and bundles of sperm cells are transferred to females.

While in females, the gestation period is generally between 21 and 30 days depending on the environmental conditions. Likewise, the   Reproduction in guppies can happen repeatedly all-round the year as females are generally ready for another cycle shortly after parturition.

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Mollies Breeding And Reproduction

Mollies like guppies are also live bearers, a feature generally common to members of Poeciliidae family. The physical appearance of male and female mollies is quite different making it easy to sex them.  In the aquarium, it is best to keep two or three females per each male as they often harass the females.

Male mollies also possess gonopodium, a modified anal fin that is used to channel sperm cells into the females. Mollies fertilization is generally internal and the fertilized eggs usually remain in the female for them to carry. This gives it a high survival rate because the eggs are neither scattered nor endangered.

They generally have a longer gestation period compared to the guppies. Their gestation period is usually around 60 days. Each fertilization cycle can see a molly give birth to 20-50 well-developed fry.

Adult mollies are usually separated from fry to prevent them from eating up the fry. Having floating plants in the aquarium can also be an alternative because it makes it easy for fry to hide from adult fish.


As much as it is highly possible to crossbreed mollies and guppies because they belong to the same family, and they have a similar breeding pattern, it is not advisable to do so.  This is because the fry from this crossbreed doesn’t survive, and if they do they are often sterile.

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