How long are Mollies pregnant? 5 pregnancy stages

pregnant molly fish

Mollies are one of the most popular pet fish to breed in an aquarium. They can produce fry (baby fish), and they usually take good care of their young. So how long are mollies pregnant?

However, mollies can also be challenging to breed successfully, especially if you’re trying to get them to have a specific number of fry.

In this article, we’ll discuss When mollies fish birth to the fry and some tips on how to increase the chances of success.

How long are mollies pregnant?

How long are mollies pregnant

The gestation period for a molly fish is about 4-6 weeks, approximate 20-40 days. However, it depends on the type of moly pet you have. Some mollies may stay pregnant for up to 50-70 days. Mollies are livebearers, meaning that they give birth to live young rather than laying eggs. You may notice your molly’s belly getting larger as she gets closer to giving birth. She may also become more sluggish and have a decreased appetite.

Once your molly gives birth, you’ll see small fry swimming around in the tank. The fry is born fully formed and can fend for themselves, but they are tiny and vulnerable.

You’ll need to take steps to protect the fry from being eaten by other fish in the tank. We’ll discuss those steps below.

Molly pregnancy Stages

Molly’s pregnancy involves five main stages.

#1. Conception in Mollies

Conception occurs when the male molly fertilizes the female’s eggs. Once the eggs are fertilized, they are carried in the female’s body until they are ready to be born.

Usually, a female molly will give birth to around 20-30 fry (baby mollies) at a time.

#2. Embryo Formation

Also known as the pre-embryonic stage, starts with the fertilization of the egg and ends with implantation in the uterus.

During this stage, the embryo grows and develops within the mother’s Fallopian tube.

The gravid spot is an important clue that your fertilized egg has developed into an embryo. It will begin to form around 7 days after conception and can be seen with the naked eye as it develops within its mother’s uterus!

#3. Development of Embryo into Fry

The development of the embryo into the fry is the third stage of molly fish pregnancy. The fry will continue to develop inside the mother until they are ready to be born.

During this time, the fry will absorb nutrients from the yolk sac and develop their organs and systems. When they are fully developed, the fry will be released into the water, where they will start to swim on their own.

This process usually takes around 4 weeks but can vary depending on the species of molly fish.

#4. Pre-birthing Stage

In the pre-birth stage, a molly fish prepare itself to give birth to the fry mollies. At this stage, all the fries will be fully developed in mommy’s belly! You can see the eyes of the fry inside the molly mother’s belly at this stage.

#5. Fry Delivery Stage:

Fry delivery is the last stage of molly fish pregnancy. In this stage, the fry is born and must be released into the water. The fry delivery process can be induced by several methods, including hormone injections, changes in water temperature, or simply waiting for the fry to be born naturally.

After the fry are released into the water, they must be fed and cared for properly in order to survive. Fry delivery is a critical stage in the molly fish life cycle, and proper care must be taken to ensure that the fry survives and thrive.

How do you increase the chances of success when breeding mollies?

orange molly fish

Breeding mollies can be a rewarding experience, but it’s important to do your research and be prepared for the challenges that come with it.

Below are some of the tips that will help to increases the chances of success while breeding mollies and to prevent the fry loss.

1. Choose healthy, Compatible fish

If you’re going to breed mollies, it’s important to start with healthy, compatible fish. Avoid fish that are sick or have any obvious genetic defects.

It’s also a good idea to choose fish that are similar in size so that the female isn’t overwhelmed by the male during spawning.

2. Provide plenty of Hiding places

Once your molly gives birth, the fry will be very small and vulnerable. To increase their chances of survival, provide plenty of hiding places in your tank for them to hide from predators.

This can be something as simple as adding some live plants or pieces of driftwood.

3. Feed them live food

Newly-hatched fry is too small to eat most commercial fish foods. To ensure they get the nutrition they need, feed them live food like brine shrimp or micro worms. As they grow, you can gradually introduce other foods like pellets or flakes.

4. Keep an eye on water quality

Mollies are very sensitive to water quality, so it’s important to keep an eye on your tank water cleanliness and its temperature. Regular water changes will help to keep these levels in check.

How do I know when my molly is about to give birth?


As your molly gets close to giving birth, you may notice some physical and behavioral changes once your molly fish gets close to giving birth. Her belly will grow, and her gravid spot turns opaque.

She may eats less often than before or not at all, sometimes even hiding away in dark corners and hiding places.

She may become more sluggish and have a decreased appetite. Her belly will also start to swell as the fry develop.

Do mollies give birth all at once?

Mollies typically give birth in two or three batches over the course of a few hours. However, it’s not uncommon for them to have just one large batch.

Will mollies eat their babies?

Mollies are not known to eat their fry. However, rarely a mother molly may eat its fry. Also, other fish in the tank may. That’s why it’s important to provide plenty of hiding places for the fry once they’re born or to separate them in a breeding tank. You can also remove any fish that are known to eat fries, such as barbs or cichlids.

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FAQ: How long are Mollies pregnant?

How long can a molly hold sperm?

Mollies can store sperm for 3-6 months, so if you remove a female from a breeding tank, she may still give birth several months later. This is why it’s important to be prepared for fry, even if you haven’t seen any recent spawning activity in your tank.

What does molly fry eat?

Newly-hatched fry is too small to eat most commercial fish foods. To ensure they get the nutrition they need, feed them live food like brine shrimp or micro worms. As they grow, you can gradually introduce other foods like pellets or flakes.

When should I separate molly fry from their parents?

It’s generally best to separate molly fry from their parents as soon as they’re born. This will give them the best chance of survival and help to prevent them from being eaten by other fish in the tank.

If you don’t have a separate breeding tank, you can use a large aquarium or even a Rubbermaid container with an air stone to house the fry until they’re big enough to be returned to the main tank.

How much should a pregnant molly eat?

A pregnant molly should be fed small meals several times a day. Avoid overfeeding, as this can lead to problems with the pregnancy. If you feed your molly pet twice a day, increase the number to thrice a day in the pregnancy period.

How many babies do mollies have?

Mollies typically give birth to 10-20 fry at a time. However, they can sometimes have up to 40 fries in a single batch.

Is my molly pregnant or bloated?

There are a few physical signs that can help you to tell if your molly is pregnant or just bloated. One is the gravid spot, which is a dark area on molly’s belly that becomes more pronounced as she gets closer to giving birth. You may also notice that her belly starts to swell, and her appetite decreases.

If you’re still not sure, you can always take her to a vet or experienced aquarium keeper for an evaluation.

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