Guppies and Mollies can crossbreed under certain circumstances. The resulting babies are known as Muppies or Gollies, depending on who you ask. These babies are usually about the size of a Molly but with Guppy coloration. Unfortunately, muppies/gollies are always sterile, and can’t reproduce further generations!
For many years now guppies and mollies have been two of the most popular species of fish in the freshwater fish-keeping hobby. Both species come in a variety of colors and tail shapes, and both species are live-bearing fish, meaning they give birth to live, free-swimming baby fish.
Over the last 30 years, I have kept and bred countless numbers of both guppies and mollies, including Black Mollies, Sailfin Mollies, and Dalmation Mollies. I don’t think there has been a single day where I didn’t have a tank full of guppies, mollies, or both in my fish room.
Can Guppies And Mollies Crossbreed?
It has long been known in the hobby that Guppies and Mollies could cross-breed to give us Muppies/Gollies. For many years hobbyists have been reporting that a guppy and molly in their care have crossbred. Forums are full of such encounters.
Guppies and Mollies will only crossbreed under certain circumstances. If we keep a group of male and female guppies in a tank along with a group of male and female mollies, there is very little chance the two species will cross-breed. Both species of fish will be perfectly happy breeding with their own kind.
If, on the other hand, we keep a single male guppy with a single female molly (or visa-versa) there is a good chance the species will cross-breed, resulting in Muppies/Gollies.
What Do Muppies/Gollies Look Like?
Muppy/Golly fish are truly stunning. Imagine a 3” (7.5cm) molly, but with all the color of a guppy, and that is essentially what a muppy/golly looks like The image at the top of the page is courtesy of Carter52 on Reddit and shows what a fully grown Muppy/Golly can look like (Original Article).
Can You Breed More Muppies/Gollies?
You may be wondering why we don’t see more of these stunning fish for sale in our local aquarium stores. Unfortunately, Muppies and Gollies are always born sterile. It is not possible to breed subsequent generations from a Muppy/Golly pair.
Muppies/Gollies should be considered genetic oddities rather than a new species of fish we can all keep.
How To Care For Muppies/Gollies
If you are lucky enough to have some muppies/gollies in your care, they can be treated exactly like either a guppy or a molly. They will want the same water parameters, the same food, and the same aquarium set up as a guppy or molly would.
Guppies and Mollies CAN crossbreed. There are numerous reports of it happening. When circumstances are right, and a single guppy finds himself living in an aquarium with a single molly, there is a good chance that muppies or gollies will be the result.