Do Black Mollies Lay Eggs? (Finally Explained)

Do Black Mollies Lay Eggs? No, Black Mollies do not lay eggs. Black Mollies are a live-bearing species of fish, meaning the female retains the fertilized eggs inside her body while they develop, then gives birth to live, free-swimming baby fish.

Eating Daphnia
Eating Daphnia

Black Mollies were one of the first fish I ever bred in my fish room. I was new to fish keeping and the Black Mollies went into one of the very first aquariums I added to my fish room. I remember being surprised when the lights came on and there were baby Black Mollies swimming around the aquarium.

Black Mollies are one of the most instantly recognizable fish in the freshwater fish-keeping hobby. They are one of the species of fish often recommended to new fish keepers. If you have ever kept them, you will no doubt at some point see baby Black Mollies in the aquarium.

What Is A Live Bearing Fish?

Livebearers are a type of fish where the females retain the fertile eggs inside their bodies while they develop into fish. After a period of 30 to 35 days, female livebearing fish give birth to live, free-swimming baby fish. Most livebearing fish take no parental responsibility for their young after they are born.

Being a livebearer gives the fish an advantage over their egg-laying cousins. By safely retaining the eggs inside the female fish, there is no chance of the eggs being eaten by other fish.

Livebearers have an evolutionary advantage by giving birth to live baby fish, their babies will be bigger and develop faster compared to fish hatching from eggs.



I have bred fish for fun, for competitions, and for profit. Black Mollies are a great choice of fish to breed at home, then sell the babies or swap them with your local fish store for more fish or maybe some fish food.



How Many Babies Can A Black Mollies Give Birth To?

Female Black Mollies can give birth to anywhere between 40 and 100 babies at a time. The actual number of babies will vary depending on the age and size of the female.

A young female Black Molly may only give birth to a few baby fish, whereas an older, larger female will give birth to many more babies.

Feeding your Black Molly females a high-quality diet will help them produce more babies.

How Often Do Black Mollies Have Babies?

Female Black Mollies can give birth roughly every 35 days. The actual gestation period will depend on water temperature, with the warmer the water temperature, the shorter the gestation period.

Like some other species of livebearing fish, Black Molly females can retain some of the males’ sperm, meaning they can have more than 1 batch of babies from a single mating.

What Age Do Black Mollies Start Having Babies?

Black Molly Females can start to produce babies somewhere between 3 and 6 months of age. The younger and smaller the female, the fewer babies she will produce. As the female grows, the more babies she will produce with each spawning.

Anyone hoping to increase their Black Molly numbers, or to actively breed their Black Mollies to sell back to their local fish store, should try to raise a few females in a separate tank from the males.

If you have the patience to grow a few females in a dedicated aquarium for 12 months or so, then introduce a male to the group, you will be rewarded with large batches of fry for months, possibly years to come.

What Other Fish Are Live Bearing?

There are a surprisingly large number of other livebearing fish in the freshwater fish-keeping hobby. Guppies are the ones that most people are familiar with, but Platies, Swordtails, and Endlers Livebearer are all popular and fairly undemanding to keep.

Anyone looking to up their game and keep a slightly more challenging livebearing fish should look towards either Anableps (also known as the Four-Eyed fish) or Halfbeaks. Whilst both species are livebearing, they have their own quirks that make them a challenge. Breed one or both of them and you can call yourself a real livebearer nerd!

In Conclusion

To answer the question, ‘Do Black Mollies lay eggs?’, the answer is No, Black Mollies do not lay eggs, they are a live-bearing species of fish that give birth to live, free-swimming baby fish.

Black Mollies are an undemanding species of fish that will make a great addition to any aquarium.


About the Author

I’ve been keeping, breeding, and showing tropical fish for nearly 30 years. Over that time I’ve done it all! I’ve had great success and I’ve made some really foolish mistakes (like the time I bought an Asain Walking Catfish). Read more…
Richard James
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