Platyfish and mollies belong to the same family but have different genera: Xiphophorus and Poecilia. Rare intergeneric and interfamilial hybrids have been known to occur, which brings us to our question:
Can platyfish and molly fish breed?
Platies and mollies are not compatible to breed naturally. Fish can only crossbreed with other fish that are closely related. For example, platies can crossbreed with swordtails, while mollies can breed with guppies.
However, it is possible to interbreed platies and mollies experimentally and not naturally. Platies and mollies have a few differences though they belong to the Poeciliidae family. They share some characteristics, such as peacefulness and friendliness.
Can you mix platy fish with mollies?
Platies and mollies can mix in the same tank because they are peaceful and friendly and will get along well in an aquarium. However, male mollies can become aggressive if the tank is overcrowded.
Similarly, platies are peaceful, but overcrowding in small fish tanks makes the males more territorial and fin nippers.
To mix platies with mollies, use a fish tank bigger than ten gallons. They’ll live happily under optimal conditions because a larger tank allows each fish space. (See my guide on tank size for platies here).
When can fish interbreed?
Research by Dr. Joana Meier of St John’s College, University of Cambridge, found that “Female fish can breed a new species if they aren’t choosy about who is Mr. Right. Fish will mate with a species outside their own if the male’s coloring is attractive enough or if the female can’t see him properly.“
It is, therefore, possible that mollies and platies living in the same tank may breed under some odd circumstances:
- Female platy or molly can mate with a male of the other species if the male’s color is attractive enough.
- They can breed if the female does not see properly.
This occurrence is very unlikely, but it is possible.
You might think that the fry in your aquarium came from mating between your platies and mollies.
Scientists have also found that female platies can give birth more than once from one mating session. They have specialized cavities that store and nourish the male sperms for six months.
If you notice platy fry in your aquarium, maybe you bought a pregnant female.
However, fry that occurs six months after mixing platies and mollies might be hybrids. Note that it is the genus of the two fish species that determines whether they can breed or not.
If platies and mollies happen to mate, the hybrids produced usually lack viable sex cells and can also show stunted growth.
I’ve seen mating attempts between the opposite sexes of mollies and platies living in the same tank. However, those have never produced any fry.
What fish can platies breed with?
Tens of platy and molly varieties occur from intergeneric and interfamilial mating. Molly and platy fish varieties are distinguished by their color and fin configuration. For instance, keep variegated, pintail, or tuxedo platies together, and breeding will occur naturally.
The Xiphophorus Genetic Stock Center recognizes 26 species that can breed with platies.
Here are 5 fish that can breed with platies :
1. Green swordtails (Xiphophorus helleri)
Platies will breed with any fish in the Xiphophorus family, such as green swordtails – Xiphophorus helleri. They appear olive green in color, and adults reach about 5.5 inches in length.
Green swordtails and platies are closely related and can breed easily and produce viable and fertile fry.
2. Highland swordtail (Xiphophorus malinche)
Highland swordtails get pregnant like platies and give birth to fry. These types of fish are called livebearers.
They grow to about 2 inches long. Mollies are euryhaline, but platies and swordtails are adapted to freshwater. One fertilization between platies and highland swordtails can produce several batches of fry.
3. Chiapas swordtail (Xiphophorus alvarezi)
Chiapas swordtails can grow up to six inches in length. It is variegated with orange, green, and pearlescent white spots. The sword at the fish’s tail is usually bright green with black edges.
Like most Xiphophorus fishes, Chiapas swordtails thrive in pH 7.2 and 8.1. If you put Chiapas swordtail and platies together, they will breed since they are of the same genus.
4. Pygmy swordtail (Xiphophorus pygmaeus)
Pygmy swordtail is a dwarf fish native to Central America, Mexico, and Honduras. However, the increased ornamental fish trade has introduced the fish to more than 31 countries.
Platies can breed with dwarf swordtails. Unlike the female pygmies, the males do not possess swords. Pygmy swordtails occur in various colors, depending on their habitat.
5. Swordtail platy (Xiphophorus xiphidium)
Xiphophorus xiphidium also belongs to the Poeciliidae family. It is pretty difficult to distinguish them from platies or swordtails. But swordtail platies have a striking greenish-brown coloration which gets white towards the belly.
They are commonly called spiketail platy and will breed with platies to produce viable fry. Males grow to about 30mm, and females up to 40mm in length.
See a list of more fish that can crossbreed with platies here.
Fish that can interbreed with mollies
Here are fish that can crossbreed with molly fish:
- Guppy fish
- Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. (2022). Xiphophorus. The Animal Diversity Web (online).
- Texas State University. (2022). Xiphophorus Genetic Stock Center.
- Roberta Kwok: Science News for Students: The mixed-up world of hybrid animals