Why Is My Molly Fish Not Giving Birth? 6 Reasons Explained

Why is my Molly fish not giving birth?

Molly fish are colorful freshwater fish. They are very active fish to have in your home aquarium, but many people do complain that theirs have not reproduced, despite having males in the tanks with them, and also despite showing signs of pregnancy. This seems awkward, but it happens, and in this article, you will learn why and the possible solutions to this problem. So read to the end, to fully understand this article.

Why is my Molly fish not giving birth? Molly fish can prolong their gestation period, or not get pregnant at all if the environment is not suitable for them.

If you are new to fish keeping, you might be surprised to hear this for the first time.

Some fish, which Molly fish is among are very picky when it comes to their environment, and they will refuse to reproduce in any environment that is not favorable to them. In this article, we will discuss in detail all the factors that might prohibit them from giving birth.

One funny thing about this type of fish is, although, they might get pregnant, which you will confirm by seeing their bloated stomach, and every other sign of pregnancy, but, they won’t still give birth after 50-70 days which is their gestation period, because they have the special ability to prolong their gestation period.

Let’s see some of the reasons this might happen.

Why Is My Molly Fish Not Giving Birth?

Some of the reasons why your Molly fish could refuse to give birth are:

1. Toxins/ Chemicals in the water: We all know that no aquatic animal will survive for long, or at least live comfortably in water that contains some toxins or bad Chemicals.

Many toxins could form or breed in a tank, and endanger all the living things in it, or at least stress them, such toxins include ammonia, chlorine, copper, nitrites, nitrates, etc.

Many of these toxins are caused by poor water conditions.

Molly fish on its own is a kind of fish that despise stress of any kind. Although they are very active, and could even stress other animals when it comes to them getting stressed, they don’t like it, and when such Chemicals are present, they won’t feel comfortable in such a tank, and they might have to withhold their pregnancy because they can only give birth in a favorable environment.

The fact is, when such toxins are present, they won’t even mate, even talk of getting pregnant, but even if they mate and the female gets pregnant, she won’t still have to give birth in such a condition.

2. Stress/Bullying: As I mentioned above, they don’t like being stressed, especially the female Mollies, and when exposed to it, they might not be healthy.

Stress could come in many forms, such as bullying by the bigger fish, or being chased about by the males, even when they are pregnant, to mate with them, etc.

When a pregnant Molly is exposed to stress, she will have to prolong her gestation period, or even have to abort the pregnancy, because they can do that.

So, if your Mollies are stressed, maybe because of bullies in the tank, don’t expect them to give birth, because they could only do that when they are very comfortable, and not when stressed.

Although they are not good parents, because they do eat their babies, but upon that, if they perceive any threat or the environment is unsafe for their babies, maybe due to other aggressive animals, they won’t give birth.

3. Sometimes people do mistake a bloated stomach for pregnancy, and that might be your case.

Fish are pigs and could eat all day, for the fact they have food with them, so many people mistake their overfed fish for pregnancy because of the bloated stomach.

There are many signs of pregnancy in fish such as the bloated and the V-shaped gravid spot, overall weakness of the fish, laying at the bottom, and later on, you might start seeing some black spots in the stomach which are the fry.

When you see all these signs, then know that she is truly pregnant, so don’t miscalculate.

4. Sickness/Diseases: These are other factors that might make these fish not to give birth.

Once an animal is sick, it is automatically weak and unable to perform fully well again, and we all know that these fish could only give birth when everything is alright.

So, the problem here might be sickness. And this is one of the reasons fish die after giving birth.

5. Wrong water condition: Another factor that might cause this is wrong water parameters or poor water quality.

Mollies thrive at temperatures that are between 77 to 80 degrees F, a pH ranging from 7 to 8, hardness ranging from 20 to 30 dGH, and a tank of at least 15-20 gallons.

When their ideal water parameters are not in place, they will get uncomfortable, and won’t perform very normally.

Another thing that could cause this is dirty water or a small tank.

6. Relocating pregnant Mollies could also make them abort or prolong their gestation period, and therefore won’t give birth.

Although many people, including myself, do advocate relocating pregnant Mollies and other fish to another tank. ( breeding box)

Although it’s for their good, to curtail stress and cannibalism by other tank mates, sometimes the fish won’t understand, and they might see it as stress, whereby aborting or withholding their pregnancy.

These are the most common reasons why your Molly fish is not getting pregnant, or the already pregnant ones are not giving birth. Let us see how to tackle these issues.

How To Make Your Molly Fish To Give Birth

This article can’t be complete without telling you the solutions to this problem.

To solve this issue, first, you must identify the main causes and then tackle them with these tips.

1. Since mollies don’t like nor tolerate stress, it is better to eliminate anything that will cause them stress.

For instance, keep them at a ratio of 2-3 females per 1 male fish, for the males not to be chasing the pregnant females up and down, thereby causing stress for them.

Again, keep only Mollies, and if you must keep other animals, keep non-aggressive ones to eliminate aggression, stress, and bully.

2. Keep a favorable water condition, and with the right temperature for them.

Being tropical fish means they could only do fine in a moderate water temperature between 77-80°F, so keep to that temperature with the help of a heater.

Get them filter and water testing kits too to checkmate the toxins in the water, and do at least 20-50% water change when you notice any toxin until they are completely off your tank.

Again clean the tank at least once in 2 weeks, depending on how many fish you have in it.

3. Your tank should be planted, and with caves and substrates in place, to stem stress and possible aggression.

4. Make sure you keep a mixture of both males and females for them to mate and reproduce, because mollies are not asexual, and there is no how only the females could reproduce all by themselves.

Although in most cases, the females could all be by themselves, they do this by mating with a male, storing the sperm in their body, and using it repeatedly to fertilize their eggs inside their body.

This is why you could see a female reproduce all by herself, but this is very limited because she could no longer be able to do this once the sperm finish, and she must need to mate with a male again to have sperm to fertilize her eggs.

When Should I Separate My Pregnant Molly Fish?

As I explained above, one of the things that could cause this fish to hold her pregnancy is stress, which is sometimes caused by tank mates.

To avert this, many aquarists do suggest relocating the pregnant females to a breeding tank once she starts showing signs of delivery, like seeing the babies in her stomach.

But sometimes, it is advisable not to do this, but just get a tank divider and divide the tank, keeping her on her side.

But if you are still okay with separating her, then do it once you start seeing the babies in the stomach.

Do Mollies Reproduce Easily?

No, Mollies do not reproduce very easily in captivity, unless they are in their ideal environment.

So, if you are having problems with your Mollies in terms of reproduction, check the above reasons and also solutions too, it might help you to get them to reproduce.


The above are the reasons your mollies are not having babies in your tank, so follow the solutions and see if things could become normal for you and your fish.