Should I Separate Pregnant Molly Fish?

Isn’t it amazing to see your adoring Mollies giving birth to their babies? But till you wait for that moment, you will have to prepare and care for the pregnant Molly fish primarily. So, while caring for them, you may ask should I separate pregnant Molly fish from others? To answer the most asked question precisely, I have come up with this article to solve your dilemma.

Yes, you should separate pregnant Molly fish from others. Since Mollies usually eat whatever fits into their mouth, they will even chase and munch Molly fry like a snack if kept in the main tank. To save them immediately after they are born, it is essential to separate pregnant Molly fish from before. For separating, you can use a breeding box or net, provide enough hiding spots, or maintain a separate tank for her.

Also, other fish in the aquarium, especially male Mollies, tend to bully or chase the pregnant Molly fish that builds stress and aggression. To let your fish live peacefully, separating them is a great idea. In a way, separating pregnant Molly fish will help her live peacefully and saves Molly fry too. 

You might not get the whole idea about pregnancy in molly fish. That’s why I suggest you to read the whole article below.

How To Know If My Molly Fish Is Pregnant?

If you are a beginner aquarist, then this information can be exciting for you! Understanding pregnancy signs helps you to identify if your fish is pregnant or not. However, if you have been following Mollies closely before, you must be aware of these signs!

Like in humans, it is visible even in Mollies whether they are pregnant or not. To realize and note their pregnancy signs, it only takes you to observe the fish regularly but carefully. 

But remember, the pregnancy symptoms in Mollies are not definite soon after they mate. Once the fertilization succeeds, then the gestation period starts, where the signs of pregnancy get pretty precise.

So, here are some obvious pregnancy symptoms that help you to know if your fish is pregnant or not:

Swollen Belly

The first and most obvious symptom that you can see in a pregnant Molly fish is their swollen belly. 

Once fertilization follows, you can see a change in the abdomen area of your female Mollies.

Usually, their bellies are rounder in general. But when pregnant, it gets thicker and somewhat in square form from the round.

The belly will start increasing, where it looks like a swollen one. But in actuality, the baby inside her belly starts growing, which makes the fish belly enlarged.

Be careful; do not get confused in a pregnant Mollies belly and swollen belly in Dropsy disease.

A pregnant Molly fish will not have pinecone-like scales, redness of the skin, and fins, but fish suffering from Dropsy disease will have.

Visible Black Spots On Belly

If you can spot some black spots on your Mollies lower abdomen area, it is a prominent sign that she is pregnant.

In most of the colorful female Mollies, some black spots start appearing during pregnancy. Many aquarists believe these black spots are babies.

However, in Black Mollies, these spots are unnoticeable as the color of the fish overshadows it.

Yet, you can identify a pregnant Black Molly with their changing physical appearance and behaviors.

Unusual Eating Behavior

A pregnant Molly fish unusually eats. Meaning; she eats more than she used to in general.

Because she will be carrying babies inside her as molly fish are livebearing fish, a pregnant Molly fish eats more. It is also a clear sign for pregnancy that you can spot.

But if you are unaware of how much the fish generally consumes, this sign of pregnancy would be difficult for you to guess. 

Thus, make sure you analyze and provide the precise quantity of food to Mollies. It helps you to differentiate if any bulky female Molly fish has suddenly started to intake more than usual or not.

Aggression Due To Pregnancy

You might have heard that female Mollies are not aggressive like the males. But this case is not reliable when she is pregnant.

A pregnant Molly fish can get aggressive suddenly if she feels uneasy or stressed in the pregnancy stage. It is just like experiencing mood swings in humans when a woman is expecting a child.

Should I Separate Pregnant Molly Fish From Others? Know Why?

This question might have perplexed you a lot. But the answer is quite simple. If you want your Molly Fry or baby Mollies to live and grow right after they are born, separating the pregnant Molly fish is crucial. If not, the choice is all yours!

Also, your pregnant Molly fish requires a peaceful environment to relax, which is unlikely to happen in the main tank with other fish.

So, yes, you should separate the pregnant Molly fish from others in the main tank. It saves both Molly Fry and pregnant Molly fish from many deadly disturbances.

In more precise, I have explained why you should separate pregnant Molly fish from others in brief:

Saving Molly Fry Immediately After Birth

Molly fry or baby Mollies are very small when they are born. Molly fish give birth to all the fry at once. They can be an easy meal for any fish species, including Mollies: if they stay in the main tank.

Mollies will leave no chance to chase and munch them once they notice baby Mollies in their tank.

So, it is better to separate their mother Molly fish from others before they are born to save them from this risk.

If you want to see Molly Fry growing and enduring later, you have to make a move from today. Thus, you shall separate the pregnant Molly fish from others in the tank.

Protection From Bullying Male Mollies

Not just Molly Fry, but the pregnant Molly fish is also not safe if she stays in the main tank.

Usually, male Mollies in the tank will chase and bully the females even if the fish is pregnant. Their chasing game lasts until their mating inducement gets unsatisfied.

Here, even for the pregnant Molly fish, the male Mollies tend to chase and mate often. It affects the physical and mental well-being of the fish.

To avoid this issue, separating the pregnant Molly fish right after you find out that she is expecting is vital. 

Reduce Stress

Separating Molly fish when she is pregnant also reduces the stress, which possibly builds if stayed in the main tank.

Usually, the pregnant Molly fish stays dull, lacks appetite, and rest at the expecting stage. In the main tank, the fish is likely to face stressful instants from other fish.

The stressful situation may pile up to the extreme, which affects her health and might trigger her aggression.

How Can I Separate Pregnant Molly Fish From Others?

If you are willing to see Molly Fry grow and thrive, saving them before their birth is significant. For this, you will have to separate the pregnant Molly fish primarily.

Hence, you can separate pregnant Molly fish from others by following methods:

Installing Breeding Box

If you want the pregnant Molly fish to live in the main tank but separately, installing a breeding box can be a fine idea. It is one of the best choices to separate and save the Molly fry after birth. 

A breeding box is a container made to protect the expecting Molly fish by providing a separate tank place in the tank.

In this box, the tank water runs through a water pump without troubling the fish inside it. So, your fish will certainly have no problem surviving in the box. 

Take the pregnant Molly fish and keep it in the breeding box till she gives birth. Once she gives birth to the Molly fry, the babies will fall into another section of the breeding box, leaving the mother Molly behind. 

By doing this, you can separate the pregnant Molly fish from others even after staying in the main tank. 

Hiding Spots

Another way you can separate the pregnant Molly fish in the main tank is by maintaining enough hiding spots for her.

You can separate the pregnant Molly from other fish by hiding spots like artificial plants, live plants, and other aquarium decorations

But, this method may not be effective as a breeding box set up after the birth of Molly fry. They are unlikely to last long as once they are noticeable, other fish will attack and eat them instantly.

Maintaining A Separate Tank For Pregnant Molly

A separate tank would be a definite requirement to see Molly Fry live and grow. If it is requisite after Molly Fry is born, why not prepare it from the beginning by maintaining a separate tank for pregnant Molly fish?

Yes, you can maintain another tank for pregnant Molly fish only to separate the fish from others. It will surely save your Molly Fry later and also cares for the pregnant Molly Fish throughout the gestation period.

However, there are various tank conditions required even in the separate tank.  This very tank will also act as fry tank, that’s why it is necessary to know how to set-up a fry tank.

The ideal water temperature, pH level, and aquarium water hardness are requisite in the tank. Also, some live aquarium plants, suitable filtration, and lighting would enhance the tank. 

How Long Should I Separate Pregnant Molly?

Firstly, you shall separate the pregnant Molly fish using various methods mentioned above as soon as you realize the fish is expecting.

The soonest you separate the pregnant Molly fish, the better the fish can live throughout the gestation period.

Regarding how long shall you separate the fish is until the fish gives birth to her babies. Once you see the pregnant Molly fish gives birth to Molly Fry, separate the mother Molly immediately. Put the mother Molly Fish back in its main tank with other fish. 

After Molly Fry is born, you can no longer keep the pregnant/mother Molly fish in the separated tank. Even being mother Molly, she can also eat her babies. 

Frequently Asked Questions

Here are some of the FAQs along with the answers that people often ask about.

Do Mollies Eat Their Babies?

Yes, Molly fish eat their babies. They generally eat every tiny matter that fits inside their mouth. So, even if the Molly Fry are their babies, they will still start munching them.

How Long Do Baby Mollies Need To Be Separated?

From birth to till next 21 days, it is necessary to separate baby Mollies. After keeping them in a separate tank for 14 to 21 days, you can see them growing large enough to live in the main tank without any risk.


Yes, you should separate the pregnant Molly fish from others in the main tank. By doing this, you can save Molly Fry from other fish after birth. Also, it protects the pregnant Molly fish from different stress and bullying throughout the gestation period. 

Once you see pregnancy symptoms, immediately separate the fish from others. As soon as you isolate the pregnant Molly, the more secure the fish and Molly Fry will get.

Keep your fish safe and happy!