Can A Molly And A Goldfish Mate?


If you’re in the freshwater fishkeeping hobby, you must be engrossed with all the beautiful hybrids that have resulted in cross-breeding different species. Just look at the Flowerhorn, the Endler Guppy, and the Blood Parrot. So why can’t you make yours?

Do Mollies And Goldfish Have Anything In Common?

Both Mollies and Goldfish are freshwater fish, love a little salt in their tank, and both produce a lot of waste. Both species are also omnivorous.

While they are both peaceful fish, note that these two living together would be a bad match!

Is It Possible For A Molly And A Goldfish To Mate?

Unfortunately, not all fish can mate, even with some similarities.

In this case, Mollies and Goldfishes can’t mate. These are two very different species—the Molly being from the family Poecilia and the Goldfish from the family Cyprinidae.

Fish that can cross-breed should be closely related and have tank compatibility.

Even if both are freshwater fish, Mollies and Goldfish can even hardly belong to the same tank.

Why Aren’t Mollies And Goldfish Compatible?

There are several reasons why Mollies and Goldfish can’t even stay together, much less mate.

Reason #1: Their temperature requirements are different

While some water parameters can overlap, Goldfish prefer cooler waters than Mollies do.

Mollies prefer a temperature range of 72 to 80 deg Fahrenheit, much like other tropical freshwater fish do. On the other hand, Goldfish prefer water with 65 to 74 deg Fahrenheit temperature. Any higher than this and your Goldfish might suffocate or become ill, and die.

Can a Molly and a Goldfish Mate
Can a Molly and a Goldfish Mate?

We’ve listed the water requirements for Mollies here if you want to check that out.

Reason #2: Mollies tend to bully Goldfish

It’s probably the Molly’s energy and speed, but they do like to chase and bully Goldfish around. It’s could be fun to watch… until the nipping starts! And that’s not good as compatibility also dictates that your fish won’t hurt each other.

Some joke it’s a stereotype—Mollies being the jocks with their athleticism and Goldfish being the nerds with their smarts. Put them in the same room and you know what’s going to happen. Some even say it’s the orange-reddish color that, like a toro to a matador’s muleta (cloak), puts the target right smack on the goldfish’s rounded body.

If you want to know how Mollies react to other kinds of tankmates, you can read all about it on our post here.

Reason #3: Goldfish are a lot slower than Mollies

Pairing Goldfish with Mollies will result in the latter eating all the food. Although they can thrive on the same diet, the Goldfish would have a hard time competing with the Mollies for resources because of their (Mollies’) sheer speed and personality.

Reason #4: Mollies are livebearers, Goldfish are egg-layers

Belonging to different families altogether means they have different body structures that require different fertilization methods. A male Molly will insert his sperm into the female Molly’s body where internal fertilization takes place. She will then give gestate and give birth to live young after 6 to 10 weeks.

On the other hand, female Goldfish lay eggs and the males fertilize them with his milt (sperm) wherever these eggs get stuck. They then hatch after several days.

Even if you put a single Molly and Goldfish together in one tank, they won’t even consider hanging out together to become friends.

Reason #5: Their similarity is their incompatibility

One of the things we mentioned above was that both species poop a lot. Creating a lot of waste together will be a disaster in a single tank. Messy fish will require you to change, clean, and test water often. That’s very high maintenance right there.

Too much waste in the water causes stress and illnesses in fish. If you don’t clean as often as you should, your whole tank will fail as the number of bacteria present won’t be able to process all of that ammonia in the water. Ammonia and nitrite spikes are always toxic to fish.

Reason #6: Goldfish grow large

Fancy Goldfish remain relatively small. Mature sizes are about 6 inches or so.

However, some varieties of Goldfish grow up to 14 inches long. You may have bought them while they were an inch long for a mere 99 cents, but you’ll be surprised by how much they grow over the years.

Since the ideal minimum number of Goldfish is a pair, you will need at least 100 gallons of tank space for them alone. This is why a lot of people like taking care of Goldfish in ponds along with—you guessed it—Koi.

What Can Mollies and Goldfish Breed With?

The best (and most obvious) fish that each of these can breed with are the same kinds. There are many different kinds of Mollies, such as the Sailfins, the Balloons, Dalmatians, Gold Dust, Black, Lyretail, and so much more. All of these are the same species and will readily interbreed with one another.

Goldfish
What Can Mollies and Goldfish Breed With?

The only way a Molly can mate outside of its species is if it were with the same family Poecilia. Species included in this family are fellow livebearers Guppies, Endlers, and Swordtails. However, only Guppies will qualify to interbreed with Mollies because Endlers and Swordtails have a different gonopodium shape.

When cross-breeding, it is recommended that the female be a Molly as a female Guppy is too small to carry Molly babies. Female Guppies might die giving birth to Molly babies.

The resulting hybrids, which breeders fondly call Muppies, are sterile. Thus, it cannot breed with other Muppies, Mollies, or Guppies. They do look more like Guppies but with blue and brown combinations. A rarer additional color is green.

At the same time, Goldfish have different varieties—all of which are beautiful and will readily mate with each other. There are the Orandas, Comets, Shubunkins, Fancy Goldfish, Telescope Eye, Black Moor, Bubble Eye, Celestial, Fantail, Lionhead, Veiltail, Nymph, and so many more. The fact is, there are around 200 varieties of Goldfish!

The only other species that can interbreed with Goldfish belong to the same Carp or Cyprinidae family. These include Koi and the Common Carp. Hybrids usually come out looking gray with some copper flecks on their bodies. Some have olive coloring.

Unfortunately, hybrids produced through cross-breeding with the Goldfish are sterile, too.

The Better Choice

Instead of cross-breeding different kinds of fish, interbreeding can be a better option. Additional information on this can be read here.

Interbreeding and outbreeding will not only give you better chances of success, but you can strengthen preferred traits in the fish as well. The fact that cross-breeding Mollies or Goldfish produce only sterile fry tells you that hybrids are at a disadvantage already. Not only can they not reproduce, but they may come out looking defective and suffering.

Mollies and Goldfish have similarities, but they are incompatible to breed or even become tankmates. For more pointers on compatibility, take a look at what we shared here. Learning is key to improving at this hobby, and the bottom line will always be the welfare of the fish.

We’d like to congratulate you for doing your research before you cross-breed different kinds of fish or even put them together. We encourage you to continue to be the smart and responsible fishkeeper that you are.

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