Can Guppies And Mollies Crossbreed? (And How To Breed The Two)

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Quite frequently, people ask me questions about different combinations in fish tanks. One of the most common ones is whether guppies and mollies can crossbreed. Over the years, I gained some knowledge in this field and was even able to raise hybrid offspring. Now, I am willing to share what I learned.

Guppies and mollies can crossbreed since they both belong to the Poecilia genus. Also, these two species are compatible tankmates and, therefore, can reproduce peacefully. However, the hybrid offspring will be vulnerable, more prone to diseases, and won’t be capable of producing their own fry.

As we move forward, I will show you the steps you should take to crossbreed mollies and guppies. Even though their offspring are sterile, it is still interesting to raise their hybrids. Then, I will show you what fish can breed with guppies and what fish can reproduce with mollies.

Can Guppies And Mollies Breed Together?

The technical answer is ‘Yes’. You can crossbreed guppies and mollies. The practical answer is ‘Sort Of’. Generally, there are three factors you should consider:

1. Guppies And Mollies Are Compatible Tankmates

Mollies and guppies are compatible with one another; that is to say, they can coexist in the same tank.[1] This is important because two fish species cannot crossbreed unless they can live in the same water.

In this case, mollies and guppies are equally peaceful and social. They will appreciate one another’s company. More importantly, they have similar requirements where the water chemistry and parameters are concerned.

Guppies require temperatures of 72 to 84 degrees F and a pH of 5.5 to 8.5.[2] With mollies, you are expected to maintain a pH of 7.5 to 8.5 and a temperature of 72 to 78 degrees F.[3] As you can see, both creatures can survive and even thrive within the same aquatic environment.

They are both omnivores and might create complications in tanks with aggressive mollies and guppies because they are more likely to fight one another for food, possibly even territory. But for the most part, where their coexistence is concerned, you have nothing to worry about.

Also Read: Can Molly Fish And Guppies Live Together?

2. Both Species Are Livebearers

Both species are livebearers, which means that they give birth to live fish. This factor supports crossbreeding. In both cases, you need a male and a female fish. The female fish, be it mollies or guppies, cannot conceive unless a male fish fertilizes its eggs.

It is also worth noting that both species are enthusiastic breeders. It doesn’t take much to get them to mate, not only with their kind but with other species. In fact, the only thing you need to do to initiate breeding among guppies and mollies is to place them in a tank with fish of the opposite gender. 

You don’t have to coerce them to mate. If anything, you are expected to ensure that every male has at least two or three females on hand. Otherwise, the playfulness associated with their mating behavior could evolve into bullying and harassment.

3. Guppies And Mollies Can Produce Offspring

Again, as was mentioned before, the only accurate answer you will get from a professional aquarist is ‘sort of’. What does this mean? First of all, mollies and guppies are capable of mating. If you place one fish from each species in a tank and have both a male and a female fish, mating will most likely occur. 

This is especially true in tanks where they don’t have any other viable mating options. Guppies have no reason to reject mollies as potential mating partners. The reverse is just as true. Barring a few expectations, male mollies will happily court female guppies.

But that isn’t the end of the discussion. The mating process is merely the first stage. What happens when the female fish becomes pregnant? This is where complications emerge. The fry that are born as a result of crossbreeding between mollies and guppies are rarely viable.

Some of them die during birth. Others pass away shortly after birth because they are too weak. Those rare fry that survive to adulthood are usually sterile.[4] They won’t produce more offspring. Their line will cease to exist once they die.

This is the reason why professional aquarists are hesitant to say that crossbreeding between mollies and guppies is possible. Even in the best of circumstances, the experiment cannot produce lasting results. You cannot produce a tank full of hybrids by crossing guppies and mollies, not when their offspring are destined to be sick and sterile.

Has Anyone Ever Produced Viable Molly/Guppy Hybrids?

This question generates a lot of controversy in aquarist cycles. This is because the fish-rearing community as a whole has failed to reach a consensus on whether or not successful molly/guppy crossbreeding is possible.

It is generally believed that molly/guppy crossbreeding results in non-viable and sterile fry. However, many aquarists continue to argue that they have produced healthy fish by crossbreeding mollies and guppies.

And yet, you will be hard-pressed to find tangible evidence proving the existence of healthy molly/guppy hybrids. The people who criticize these claims are convinced that such rumors are propagated by amateur aquarists who do not realize that mollies and guppies can store sperm for months at a time.

Whenever they buy female fish from a store, once those female fish produce fry in the absence of a male fish from their species, the amateurs in question cannot help but assume that their female fish mated with a male fish from a different species.

Some people have gone so far as to present pictures of their molly/guppy hybrids. However, the authenticity of those pictures is often dismissed. Until a credible institute performs rigorous tests to either prove or disprove the myths surrounding this issue, there is no way to definitively determine whether or not anyone has produced viable fry by crossbreeding mollies and guppies.

How to Breed Guppies and Mollies?

The easiest way to determine whether you can produce viable molly/guppy hybrids is to crossbreed the two species yourself. Even though the offspring are less likely to survive or produce their own fry, you can still try to crossbreed guppies and mollies.

The process typically involves the following:

  • First of all, you need to get the right fish for your project. Mollies and guppies come in various types and colors. What kind of hybrid do you wish to produce? The results you want will determine the mollies and guppies you will crossbreed.

The key is to acquire parents whose characteristics can generate the attributes you want to see in their fry. Some stores provide detailed information explaining the genetic makeup of their fish. If you have some experience with selective breeding, you can use this information to either add or eliminate specific characteristics from your molly/guppy hybrids.[5]

  • Gender matters. You need at least one fish from either species to initiate mating. However, for the best results, you should pair male guppies with female mollies. Because mollies are larger than guppies, the fry produced by a male molly’s sperm would be too large for a female guppy to carry safely.
  • The numbers also matter. You need two to three female mollies for every male guppy. This will prevent violent conflicts from breaking out in the tank. To ensure that crossbreeding occurs, you should also limit the inhabitants of your tank to the male guppies and female mollies you want to crossbreed. Don’t distract your mollies and guppies by adding other fish.
  • Maintain the appropriate conditions in the tank. Keep the temperature between 70 and 76 degrees F.[6] Perform regular water changes to prevent toxins from accumulating – test for nitrites, ammonia, chlorine, and any other element that might disrupt the breeding process.

When it comes to your aquarium’s conditions, I highly recommend getting the API Aquarium Test Kit (link to Amazon). You can accurately measure the pH, ammonia, nitrates, and nitrites in your tank with that bundle. Within five minutes, you’ll know if something went wrong.

  • Keep an eye on the females. Look for signs of pregnancy. That includes a swollen belly and the presence of a gravid spot. If your goal is to protect the fry, you should place the pregnant fish in birthing tanks. This will protect their young ones.
  • Mollies and guppies are poor parents. They eat their fry all the time. Wait for the mother to give birth to the fry and then remove her from the birthing tank.[7] Like the adult fish, the offspring require a well-maintained tank with a temperature, pH, and hardness appropriate for their species.
  • Give them a balanced diet that includes flakes, flies, and bloodworms. Fry eat more frequently than their adult counterparts. They cannot survive unless you satisfy their appetite. You don’t have to worry as much about overfeeding in such cases.

At the end of the day, even with the best care, your molly/guppy hybrids could still die. You have no way of guaranteeing their survival. As far as most aquarists are concerned, it is currently impossible to crossbreed mollies and guppies in a way that results in healthy hybrids. But that shouldn’t stop you from trying.

Also Read: Guppies Chasing Platy And Molly Fish

What Fish Can Breed With Guppies?

Guppies can breed with fish from the Poecilia genus, including mollies, endlers, and different guppies species. However, while guppies can potentially crossbreed with mollies and endlers, the hybrid offspring will be sterile, which means they won’t be able to reproduce their own fry.

Guppies and endlers have a lot in common. Some aquarists have argued that crossbreeding between the two can produce viable fry. However, just like the molly/guppy controversy, these claims have also been disputed.

What Fish Can Breed With Mollies?

Mollies can breed with fish from the Poecilia genus. That includes guppies, endlers, and different mollies subtypes. However, it is better to breed mollies with their own kind. If you try to produce mollies/guppies or mollies/endlers hybrids, the offspring are less likely to be variable or fertile.

When it comes to breeding, I suggest considering different types of mollies. It doesn’t matter whether you have a black sailfin molly, a Dalmatian molly, or a golden sailfin molly. Because they are all part of the same species, they can breed successfully.[8]


If you put guppies and mollies in the same tank, they will probably crossbreed. The best way to achieve that is to keep two to three female mollies for every male guppy. You should also make sure that the water parameters are ideal for both creatures and that there are no aggressive tankmates nearby.

However, in the end, their hybrids are less likely to survive. They will be extremely vulnerable and prone to diseases. Also, the offspring won’t be able to reproduce on their own. That is because fish should stick with their species when it comes to reproduction.

On that matter, you can easily breed different kinds of guppies, and the same is true for mollies. In this case, the offspring will be fertile and healthy. For example, you can breed Dalmatian mollies with black sailfin mollies without any issues.