Why Is My Pregnant Molly Hiding? (And What To Do About It)

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When my molly fish was pregnant, she seemed to get a little nervous and hid behind plants, rocks, and the heater. At first, I thought I had done something wrong in the aquarium setup. However, as I gained more experience in this field, I learned that this could be perfectly normal behavior.

Pregnant molly fish instinctively hide to avoid danger. As they are vulnerable at this stage, pregnant mollies choose to hide behind plants, leaves, rocks, etc. This may also be a reaction to bullying tankmates, including the male mollies themselves.

As we move forward, I will show you what steps you should take if you see that your pregnant molly fish is consistently hiding. That will ensure a stress-free environment and increase the chances of healthy fry delivery.

Also Read: Pregnant Molly Fish 101

Why Is My Pregnant Molly Hiding?

When mollies fall pregnant, their behavior changes. They can become aggressive and listless. Their penchant for hiding confuses some aquarists because they don’t know whether the fish responds naturally to the pregnancy or manifests a symptom of illness.

Unfortunately, pregnant fish can hide for various reasons. So, it isn’t always easy to identify the factors responsible for this behavior. Though, you can typically narrow your options down to the following:

1. Pregnant Mollies Are Vulnerable

For many mollies, hiding is a natural response to pregnancy. They may lash out at their tank mates during the initial stages. But as the pregnancy advances, they will become less active. 

The closer they get to their due date, the more hiding they will do. They will identify secluded locations behind objects such as plants and rocks. The goal is to give birth in peace without the interference of their tankmates.[1]

Pregnant mollies are vulnerable. They cannot fight back against predators as effectively as non-pregnant mollies. Therefore, because they are so sluggish during this period, they do not feel secure out in the open.

In fact, the last thing you want is for a pregnant molly to remain out in the open because your tank doesn’t have enough hiding places. The resulting stress could compel the fish to abort the pregnancy. 

Hiding among pregnant mollies is only problematic because pregnant mollies can die during childbirth because of stress, disease, and poor water conditions. Complications related to the birthing process can also occur. 

For instance, deformed babies can block the birthing canal.[2] Other livebearers have similar problems, including guppies. Guppies are closely related to mollies.

Because it went into hiding before it gave birth, you may not realize that your pregnant molly is dead until it has corrupted your water. Some pregnant mollies die before giving birth. Others can die after childbirth.

It is worth noting that these creatures do not always disappear during the final moments of their gestation period. 

Yes, they will go into hiding, but some of them will settle in a spot behind the most convenient plant, where you can easily see them, and they won’t move for the next few days until they give birth.

Since mollies do most of their hiding shortly before they give birth, look for signs of imminent labor. These may include the fry’s eyes in the gravid spot, typically located near the anal fin.

Also Read: How Do You Know When A Molly Will Give Birth?

2. Your Pregnant Molly Avoids The Males

Male mollies are enthusiastic breeders. This is why you need 2 to 3 females for every male. A male molly can harass a female molly to death unless you distract the male fish by adding more females.

Pregnancy won’t stop a male molly from mating with the female. Male and female mollies will chase each other around during their mating session. This behavior looks like aggression, but it’s innocent and playful.

However, pregnant females do not have the strength to contend with the attention of a male fish. As was mentioned earlier, the stress may kill them. Females will hide during their gestation period because they can’t defend themselves against their male counterparts.

They will stay in hiding until they give birth. If the aquarium doesn’t have enough females, the male fish may track the pregnant female down. 

3. There Are Bullies In Your Tank

You must keep the mollies with suitable tankmates such as platys, swordtails, and shrimp.[3] You don’t want pregnant mollies to share their aquatic environment with barbs, goldfish, and bettas.[4]

Because the pregnant mollies are vulnerable, they will stay in hiding to avoid the attention of tankmates that may attack them while they are too weak to fight back. 

4. You Have Accidently Stressed Your Molly

It is common practice to move a pregnant molly to a separate tank to protect the fry from predators once the mother pops them out. Some people will transport the pregnant molly to an entirely separate tank. Others will use breeder boxes, nets, and dividers.

These tools and techniques are necessary to keep the pregnant molly and its offspring safe. However, they can also cause stress. This is why some aquarists discourage the practice.

They don’t want beginners to move their pregnant mollies when they are about to give birth. The stress will send the fish into hiding. This is the best-case scenario. In the worst case, the fish could miscarry. 

Also Read: How Can You Tell If A Molly Is About To Give Birth?

You are better off leaving the female in the main tank and then adding objects that it can use to stay out of sight. You can scoop the fry out of the tank when they are born.

This is tricky because you have to pay close attention to the aquarium. If the pregnant molly gives birth while you’re away, the adult fish could eat the babies before you notice. This is why some aquarists move their fish the moment they realize that the creatures are pregnant.

The mollies are stronger during the earliest stages of their gestation period, and they are less likely to succumb to the stress of moving to a separate tank.

If you moved the pregnant molly and it started showing signs of stress, you can move it back to the original tank. The anxiety may subside because the fish is back in a familiar environment.

5. Your Molly Fish Is Carrying A Disease

A disease can keep a pregnant molly in hiding for longer than expected. If the fish is several weeks away from giving birth or has already given birth, but it has chosen to remain in hiding, look for signs of illness.

Symptoms like loss of appetite and weakness are common signs of a pregnant molly fish. Therefore, I suggest that you look for more specific signs such as erratic swimming, clamped fins, and labored breathing.[5]

Some illnesses will change the color of the molly fish. Others will create skin lesions, curved spines, cysts, and tumors. Ich creates white spots all over the molly’s body. Velvet disease covers the creature’s body with gold-colored cysts. Fin rot shreds the fins.[6]

Consult a vet if you don’t know how to diagnose a fish. They can determine whether the symptoms come from stress, pregnancy, or actual diseases. They can also determine whether or not the pregnant molly’s tendency to hide is a cause for concern. 

What To Do If My Pregnant Molly Fish Is Hiding?

Since pregnant molly fish are vulnerable, you mustn’t take any aggressive measures once you see that your molly is hiding. For the most part, your molly is likely to deliver independently regardless of what you decide to do.

However, if the pregnant molly shares a tank with some unwanted tankmates, including male mollies, it is best to remove them from the tank. Do that gently, without disturbing the female molly about to give birth.

If your tank doesn’t have enough hiding places, add a few decorations. I personally got the JIH Aquarium Fish Tank Decor Set (link to Amazon). It comes with plenty of artificial plants and a cave, which are excellent in relieving stress in pregnant mollies.

I also suggest considering an aquarium divider. This will allow the newborns to escape their parents once they pop out. You can also move the mother to the other side as soon as she’s done giving birth.

The last step would be testing the water parameters. I personally use the API Water Test Kit (link to Amazon) for this purpose. This bundle will accurately measure your pH, ammonia, nitrates, and nitrites.

These are the water parameters you should aim for with pregnant mollies:

  • Temperature: 77-80 degrees F (25-27 degrees C) 
  • pH: 6.7-8.5 
  • Hardness: 20-30 KH 
  • Ammonia & Nitrites: 0 ppm 
  • Nitrates: <20 ppm

Consider getting an aquarium conditioner if the toxins are too high, such as the well-known Seachem Prime (link to Amazon). Adding a few drops of this is better than conducting drastic water changes, especially when your molly fish is so vulnerable.


Pregnant mollies are beautiful, but they are also one of the most challenging fish to care for. This is especially true if you don’t consider how the stress of pregnancy can make them hide in the dark and quiet corners of your tank.

In order to ensure that your molly delivers her fry successfully, it is best to remove aggressive tankmates that may harass the fish. That includes the males themselves, which won’t hesitate to chase after a pregnant female.

At this point, it is best to add a few hiding places and an aquarium divider. That will relieve stress and ensure that the fry aren’t getting eaten once born. Either way, avoid making drastic changes, such as moving the pregnant fish to another tank.


  1. https://urbanfishkeeping.com/how-long-are-molly-fish-pregnant-for/
  2. https://www.bettacarefishguide.com/do-guppies-die-after-giving-birth/
  3. http://www.mollyfishcare.com/best-molly-fish-tank-mates/
  4. https://fishkeepingguide.net/molly-fish/tank-mates-for-molly-fish/
  5. https://www.theveterinarynurse.com/review/article/how-can-you-tell-when-a-fish-is-sick
  6. https://www.aquariumnexus.com/molly-fish-diseases-parasites-remedies/