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How To Stop Mollies From Breeding | A Simple Way |

How to stop mollies from breeding, and why do they breed fast? Mollies are livebearers and have a fast-breeding rate. So, if you have several mollies in your tank, it is hard to stop them from breeding UNLESS you know what to do.

So, you have a perfect tank with the right amount of mollies in it, and a few days later, you see several baby mollies in your tank. While seeing some new life can be exciting, the next thing that comes into your mind is, will your tank be enough for all of your baby fish once they grow up.

This article explains how to stop them from breeding and what to do if they breed.

How To Stop Mollies From Breeding

Do mollies breed easily?

Yes. Mollies are livebearers. Unlike egg-laying fish, mollies give birth to fish fry.

They fertilize their eggs inside the female’s body and give birth to live baby fish. So, the survival rate of these fish fry is higher than the eggs that fertilize via external fertilization.

Further, mollies have a remarkable ability to store male sperm in females’ bodies for months after intercourse. This means they can give birth to fish fry even if there are no male fish in the tank.

Mollies are one of the easiest fish species to breed.

Many people buy one or two mollies, but they do not understand that this fish is ready to give birth to baby fish in a few days.

How often do mollies breed?

The gestation period of mollies is around 60 days, and they breed at least four times a year.

As female molly fish can store sperms in her body for months, she can fertilize the eggs as soon as they develop. So, she may give birth to fish fry every 30 days or so.

They can give birth to baby fish in one go, but they do not always give birth to the babies at once. Some of the babies are stillborn. However, a female molly can give birth to 10 to 60 live babies at a time.

How old do mollies breed?

Mollies will sexually mature within eight weeks of their life. Once they are sexually mature, they will start breeding.

So, if you don’t want your fish to reproduce, you will have to separate the male from the female before they are eight weeks old.

How to identify male mollies from female mollies?

Identifying male and female mollies is quite easy. They do show sexual dimorphism, and both sexes have different behavior patterns.

  1. Body-color – Male mollies are usually brighter and bolder than female molies. Female mollies have rather dull color morphs, and this difference is distinct in all molly species.
  2. Size and shape – Male mollies are usually larger than females but slender than females. On the other hand, female mollies are rounder and have a significant belly.
  3. Dorsal fin – Dorsal fin of male mollies is larger than females. This will give the male molly a more attractive look to attract females.
  4. Anal fin – The anal fin of the male specimen is larger and longer than the female molly, and it is modified into a tube-like shape (Gonopodium) to copulate with the females. The anal fin of females has a triangular shape.
  5. Behavior – Male mollies always try to seek females’ attention by chasing them and swimming in front of them. Female mollies are relatively calm and stay within the group.

Why does my female molly keep having babies without male mollies?

As we mentioned before, female mollies can keep the sperms in their body for months without using them to fertilize the eggs.

This helps them reproduce even if there are no male fish in the tank. So, if you have a female molly, you should separate it from your male fish before eight weeks of age.

Otherwise, the mollies will spawn in your tank, and the female will store sperms for future use.

When you separate females after they spawned, it will be no use as they already have sperms to reproduce their species. This is why female mollies keep having babies without male mollies.

How do you tell if my mollies are mating?

Mollies usually breed in mid-water. You can spot them swimming back and forth or chasing each other.

The male molly will try to get the female’s attention by stalking her, swimming in front of her, and showing off his bright body.

If the female is ready to spawn, she will follow the male and stay a few inches behind him. Then the male will try to insert the gonopodium into the female anal fin. Once inserted, the male will release the sperm into the female’s body.

What do you do with a pregnant molly?

A pregnant molly usually will have a larger body than other females. If you suspect one of your female mollies is pregnant, it is better to separate the pregnant molly to a breeder tank.

This way, you will not have to deal with a large number of fries in your main tank.

Can molly fry survive in a community tank?

Molly fries can usually survive in a community tank if the tank has lots of hiding places such as caves, plants, and rocks.

The best way to ensure that the molly fry survives in your community tank is to feed them baby brine shrimp as early as two weeks after birth. You can also provide your molly fry fish flakes or pellets.

But, if you need to get rid of them, simply restrain from feeding your fish for several days, and your adult fish will take care of the problem for you.

How to stop mollies from breeding?

The most efficient way to stop mollies from breeding is to separate the female fish from males before they are eight weeks old.

This can be challenging if you want to keep your molly fry in the same tank because it can be hard to spot which fish are males and which ones are females.

It is usually not effective to separate the male fish after eight weeks old because mollies can store sperm for up to five months without using it. This can lead to a large number of fish in your tank.

You can also make your tank conditions unfavorable for breeding. You can minimize fish breeding by lowering the water temperature to 71 to 72 degrees Fahrenheit and reducing the water level to four inches.

You can also remove plants, decorations, and live foods from your tank so that the fry won’t have any hiding places to survive.

Further, lowering the protein intake will also decrease the fish breeding process. Mollies require protein in order to reproduce successfully. If your fish don’t get enough protein, their breeding process will slow down considerably.

What if your molly has already spawned?

There is no way to prevent your fish from having babies if they are already spawned. Sooner or later, you will have lots of molly fry in your tank. In this case, you have two options.

  1. Culling the fish fry
  2. Give or sell them away

Culling the fish fry

While this seems inhumane, you may have no other choice other than to kill your fish fry.

By that means, you don’t have to take the fish fry away and get rid of them with your hands. You can simply reduce the feedings of your adult fish, and your fish will take care of the rest.

Mollies are known to be bad parents. They practice cannibalism by eating their fish fry. So, reducing the feeding for your fish may be all you need to do to decrease the number of fry in your tank.

Give or sell them away

If you don’t want to kill your fish fry, you may consider giving them away.

It is not advisable to release the molly fry into the wild as they have been raised in a community tank and are thus unlikely to survive.

If you want to give them away, ask around first. You might find someone who has a pond and would like to raise the fry instead. Another option is selling them.

You can sell molly fry for as low as $0.25 each to your local pet store. If you don’t want to do that, you can also sell them to your friends or relatives. Since molly fry is cheap, you will be able to sell them off easily.


Mollies are livebearers and have a fast-breeding rate. If you don’t have a spacious tank to raise molly babies, it is important to stop mollies from breeding.

There are several options you can look into. With enough patience, you will be able to get rid of molly fry without harming them.

Credit to : Your Fish Guide
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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.