How to Breed Mollies & Caring Pregnant Molly [The Right Way]

How to Breed Mollies & Caring Pregnant Molly [The Right Way]

breeding mollies

Molly Fishes have a very peaceful temperament which makes them the best choice for keeping in community tanks and aquariums. They are ideal to keep in homely aquariums or tanks sizes according to their breeding perspectives. They are considered to be one of the best choices from livebearers. Mollies can breed very easily and might be already pregnant when you bought them from the store.

What does live-bearer mean?

As I have already said mollies are livebearers. This means that they can give birth to fry fishes and the process of offspring’s development has occurred through internal fertilization.

Live bearing Mollies

Fry Fishes are actually the small-sized same looking copies of adult fishes. But fry fishes can be of different colors and shapes than their parent fishes depending upon the types of fishes that mate with each other.

Many popular aquarium fishes are livebearers like swordtail, guppy, platyfish, gambusias, molly fishes and many more.

But the most common community livebearer fishes are considered to be guppies and molly fishes because both of these fishes are more peaceful than any other aquarium fishes. And even guppies and mollies can also breed with each other.


Molly Fishes breed by using the internal fertilization procedure. After the mating of male and female mollies, the ejaculation of male molly allows fertilizing eggs inside the female molly.

internal reproduction in mollies

These eggs remain inside the female molly until the fry mollies are prepared enough and released from the eggs. Then the female mollies give birth to the fry mollies.

Breeding Age:

Fishes became reproductive at a very early age. And in most cases, male fishes take more time span for reproduction than the females.

In the case of mollies, the reproduction age varies from every kind of mollies. But in approximation, Male Mollies can become reproductive at the age when they are about 12 months old while female molly fish usually becomes reproductive in half of the age of male mollies, which means they can become reproductive at the age of about 6 months.

Breeding Time:

Breeding time starts when molly fishes started the process of fertilizing the eggs. It is the duration mollies take to give birth to the babies.

The breeding cycle in mollies usually remains for approximately 3 to 6 weeks (20 to 40 days). As mollies give birth to the fry fishes so they will not release the babies until they are developed enough to survive without their parents and can swim and eat easily.

Gestation Time:

Most people often mix up the two terms breeding and gestation time, but these are two separate things. Gestation time is actually the time from copulation to giving birth to babies or either the fertilization process is not necessarily happening.

In simple words, gestation time is the duration in which a molly can become pregnant after copulation. On the other hand, breeding time tends to start after the fertilization becomes successful and Molly becomes pregnant.

The gestation time of a molly is approximately 60 days (8 weeks). Female mollies can store the sperm ejaculated by the mated male molly fish during copulation for up to a few months. Female Mollies can often fertilize eggs every 30 days even without the presence of any male molly fish in the tank or aquarium.

How Mollies Behave while Breeding?

Different fishes have different behavioral patterns of breeding. Male and female fishes both need sexual intercourse or copulation once they reached the age of their maturity. Breeding behaviors in mollies are usually noticed when the male molly goes under the female molly and copulate in order to fertilize eggs.

Chasing Behavior for Breeding:

Fishes mate after chasing their targeted fish. Either a male or female or both the male and female can chase each other. Chasing behaviors of fishes also vary from species to species but in most species either both can chase for copulation or a male mostly.

Mollies Behaviour while Breeding

In the case of mollies, both male and female mollies can chase each other. While keeping a male with multiple female mollies, the male can mate with all the females easily at different times. That’s actually the reason that a female molly is usually always pregnant when kept with male mollies.

Well, it does not clearly have a definite definition to notice the chasing behavior of mollies. But if you have mollies you can easily notice their chasing behavior.

Even I have noticed my mollies chasing behavior while writing this article so that I must be sure what I am conveying you are actually true or not. After some research and personally experiencing the chasing behavior, I have noticed that in most cases male molly usually chases the female for mating.

As it’s the nature of mostly males in almost every living being. But female mollies also chase the male or give positive signs for mating.

Usually, a female goes vertical when she agrees to mate but I have noticed that the male mollies continue to chase the ones who are swimming away from them. Even if a female swims slowly it’s also the sign that she is agreeing to mate and allowing the male to chase her easily.

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Copulation Time:

Copulation means sexual intercourse which changes from every species of fishes. Most fishes can usually copulate all the time. Likewise, mollies can also copulate all the time but they mostly copulate during the early mornings.

How do Mollies Mate?

Mollies can mate very easily, just allow them to mate. Male mollies with the bold color patterns, bigger fins and larger in size actually lead their way. So it’s better to keep one male molly fish with multiple female mollies.

One male molly can easily mate with multiple mollies. The copulation or sexual intercourse of the mollies can be noticed when a male molly fish goes under the female molly.
Molly Babies

In the case of successful mating, mollies can give birth to babies within a few weeks. Mostly after mating female is separated into a separate box which is the so-called breeding box.

I would like to recommend you buying marina hang on breeding box  costing only 9$, which i am using for my self for successful birth of babies:

marina hangon breeding box


During the process of copulation, the male molly uses its gonopodium to fertilize a female molly.

The gonopodium is the male’s anal fin to hook up with the female urogenital vent or opening to ejaculate in order to bring successful fertilization.

Molly Fish Eggs

Many of the fishes can lay thousands of eggs at a time. ‘Fecundity’ is the term used to define the capacity of fishes to lay eggs. Fecundity changes from every variety of fish.

Fish Eggs Inside Mollies

The fish that release their eggs in the open water and don’t need to care about their eggs very much have very high fecundity.

While the fishes who have to build nests to guard their eggs cannot lay many eggs at a time, hence they have low fecundity.

But mollies don’t actually lay eggs; they give birth to the fry fishes. The process of fertilizing eggs takes place inside the female molly and after the complete formation of babies, they come out of their eggs and then female mollies give birth to their offsprings.

In this way, mollies don’t usually need to guard their eggs and fry fishes are like the small-sized copies of adult fishes which can feed and care themselves.

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Pregnancy Symptoms 

Pregnancy behaviors of all the fishes are quite different among species. Most of the fishes usually don’t show any strong and bold signs when they are in their labor. But some fishes do show strong signs and behavioral changes during labor.

pregnanent molly fish

Pregnant mollies can be identified by their enlarged abdomen. Considering the behavioral symptoms of mollies pregnancy, they started searching for shelters or dark places in aquariums or tanks to hide. They usually hide under the plants if the aquarium has some.

Caring Pregnant mollies:

Mollies usually don’t need special care during their pregnancy but it’s better to provide the pregnant mollies with the desired shelters as they are always looking for some kind of darker and peaceful hiding space. Make them available enough dark space to relax.

Dark tank for pregnent mollies

If these conditions are not available in your usual tank then you must keep them in a separate aquarium with the place for them to stay hidden and place the tank in darkness. Pregnant mollies also feel more relaxed in the warmer water than the normal tank’s temperature.

Flora is a Fish Parent & Enthusiast for over 10 Years. She has Deep Love & Affection for Fish Keeping. It's become her Passion to Help others. Stay Tuned with her Blog to Know more about Pet Care Tips, Product Reviews, and Guides. If you've anything Interesting to Share about your Fish. She'd Love to Know.