Molly Fish Pregnant: Signs that your Molly is Going to Give Birth

If you are a beginner at managing a home aquarium, Mollies are the easiest to care for. They are versatile, easy to handle, and very adaptable. Besides their general care, mollies are very easy to breed too. So, if you want to experience them giving birth, the chances are that they will happen soon after.

Mollies have a short gestation period, following which they can give birth to the fries. Typically, they give birth to 20-70 fries. However, only a handful survive since they are easy to prey on.

This article will explore everything about Molly fish, their breeding, pregnancy, and the processes.

How To Tell If a Molly Fish Is Pregnant?

When it comes to Molly fish, you can only tell if they are pregnant by physically looking at them. Since Mollies are small and grow up to 8-12 cm in length, it is easy to spot pregnant. The female mollies have iridescent and slender bodies.

Pregnant Molly Fish

So, when they get pregnant, noticing an abdominal bulge is easy. Let us explore some of the most common physical signs of pregnancy in a molly fish:

Belly changes

The first sign of pregnancy is with the changing belly shape and size. The typical female mollies have a round belly. However, the pregnant ones witness more tautness to their belly. The abdominal region starts changing to a squarer shape.

Black lines

Black lines through the length of the fish are a visible sign of pregnancy in mollies. This is more prominent in the species with a lighter-colored body. You can also spot potent black spots around the anal region in the pregnant mollies.

Increased appetite

Another common sign that your molly is pregnant is with their changing appetite. If they are eating more than usual, it is a sign of pregnancy. It would help if you were vigilant about their feeding. It could also be overeating masking as a pregnancy symptom.

If you notice these physical changes in your molly, it is ideal that you keep an eye out. Sometimes, it is difficult to distinguish pregnancy symptoms from other common diseases. So, being mindful is perfect.

How Long Does It Take Molly Give Birth?

Mollies are livebearers. So, their gestation period is generally between 30-40 days, following which they give birth to the fries or the young ones. Once the molly reaches full-term of their pregnancy, it takes them a day to give birth.

As for the number of fries, a typical pregnancy can result in 20-100 fries. However, not many survive by the end. Since mollies themselves have no parental instinct, they often prey on their fries. It is thus crucial to remove the parent mollies after birth.

One unique feature about breeding mollies is that they store the sperm. They can store the sperms for months straight. But that’s not it. They can fertilize their eggs every 30 days using the stored sperm in their bodies.

Also, the white sailfin molly has the shortest gestation period of 21 days. The Dalmation molly has the longest with 60 days.

How Mollies Act Before Giving Birth?

Much like any other pregnancy on this planet, even Mollies slow down a few days before giving birth. This is to take some time for themselves, relax and gear up towards the big day. As an aquarist, you can also notice the gravid spot on their body during these last few days of gestation.

Also, if the molly has an iridescent and transparent body, you should distinguish the babies by now. As the mollies are inching close to giving birth, they constantly seek security and safety. You will often find them showing signs of aggression too. This is because they don’t want their hiding spots revealed.

If the aggression becomes out of hand, separate the pregnant molly into another tank. This will calm them down and enable them to focus solely on giving birth. The belly of the molly right before birth becomes heavy, round, and bulging too.

Signs That Your Molly Is Going to Give Birth

Once you record the behavior of the molly, you’ll know when they are about to give birth. More than the physical signs, keep track of the behavioral signs.

Giving birth is a very vulnerable and crucial time for molly. She will need a secure and safe spot to give birth. We’d recommend shifting the mollies to the breeding tank if you notice drastic behavioral changes.

Here’s what you need to look for:

Less activity

As the mollies near giving birth, you will notice a drastic drop in their activity levels. They will start being in one spot, hide away in the tank most of the day. This saves energy for the birth and ensures that the birth is safe.

Constantly hiding

If your tank has a lot of hiding spots, that’s where you will find your pregnant molly. Finding a safe spot for giving birth is a maternal instinct. So, plants, caves, bridges, props, etc., become good hiding spots for your molly.

Lacking appetite

While mollies become voracious eaters during pregnancy, it becomes the opposite when they give birth. They completely lose their appetite and start becoming less active in the tank.

How to Save Molly Fry?

Mollies aren’t the most maternal towards their fries. So, once they give birth, that is pretty much it with their responsibilities. So, if you leave a pregnant molly in a community tank to give birth, the chances are that none of the fries will survive.

However, if you don’t have the space for a separate breeding tank, invest in a breeding box. Let us walk you through these care instructions individually.

Install a breeding box

A breeding box is a small open-end box that you can hang inside the aquarium to isolate the pregnant molly. The breeding box has small holes in the bottom that allow the fries to escape and grow in the tank independently. Also, when installing a breeding box, fill it with plants too. This makes the new area comfortable for the pregnant molly.

We’d recommend keeping the breeding box in an empty tank instead of a community tank. If the fries escape the breeding box into the tank with other fish species, they will soon become prey. It would help keep the fry separate from other species until they are grown enough. During this time, feed them fish flakes and brine shrimp.

Set up a separate tank

As we said, installing the breeding box in a separate tank is ideal. Also, even if you install an independent tank for the fries and pregnant molly, ensure the water parameters are ideal.

Having lots of live plants

Pregnant mollies need constant safety and security while giving birth. The live aquatic plants provide hiding spots for them. These plants are also ideal for shielding the fries after their birth. So, don’t forget to add many compatible live plants to the tank.

Should I separate pregnant Molly?

As cruel as it sounds, mollies will eat their babies after birth. Since the fries are too small, the mollies mistake them for food. So, whether or not you should separate the pregnant molly depends on the number of fries you want after birth.

If you wish to keep all the 20-100 fries alive, you must immediately remove the mother. You’ll also have to get rid of the other fish species from the tank. Fries can’t co-exist with any fish larger than them.

Ideally, we’d recommend keeping the fries in a separate tank till they are big and mature enough. Once they grow into their staple size, you can transfer them to the main tank to co-exist with their tankmates. 

What to Feed Baby Molly Fish?

Unlike adult molly fish, the fries need more food for quicker growth. However, they aren’t picky about what you feed them. The fine-quality fish flakes make ideal food choices. Make sure you crush them up into smaller pieces or powder before feeding.

You need to feed the baby mollies consistently up to 8 weeks after birth. This will allow them to grow into their adult selves before it is safe to co-exist with the other fish. Also, avoid overfeeding your baby mollies.

Besides flakes, baby brine shrimp food is quite popular among baby mollies. Feed them a mixture of flakes and shrimp for better protein intake.


Age for the male and female mollies can begin to breed

Male and female mollies typically take up to 8 weeks post-birth to attain sexual maturity. This applies to both males and females. Avoid letting the mollies breed before that period since that can have harmful implications for the female mollies.

What can mollies breed with?

Mollies are pretty easy to breed when it is within the same species. However, they don’t mate or breed well with external species like goldfish. You can, however, breed different types of mollies and even guppies. Also, mollies are hierarchal fish, which means they gravitate towards the dominant male fish for breeding.

Do Mollies give birth at night?

Yes, most pregnant mollies give birth at night. This feels safer for them to hide the fries and give them better chances at survival, especially in community tanks.


Distinguishing your pregnant female mollies isn’t rocket science. If you keep up with them and their habits, you should track the changes in their behavior. Always ensure that you focus on making the birth a comfortable and safe experience for the mollies. We hope this article explores all your queries and answers questions regarding mollies and their birth cycles and process.

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