Can Molly Fish Live Alone?

Why Is My Molly Fish Laying at the Bottom of the Tank?

Seeing your fish lying at the bottom of the tank can be worrying, so you may be wondering why your molly fish is doing this.

There are a few different reasons why your molly fish might be lying at the bottom of the tank, for example, they could be feeling unwell, or they may simply be resting.

In this guide, we will take a look at some of the potential reasons why your molly fish might be lying at the bottom of the tank and what you can do about it.

10 Reasons Why Molly Fish Is Lying at The Bottom of The Tank

1. Pregnancy

When a female is pregnant, she tends to rest at the bottom of the tank more frequently.

This happens because the weight of the fry starts to put pressure on her swim bladder, making it difficult for her to swim around. So, she prefers to lie at the bottom where she feels more comfortable.

You can determine if your molly is pregnant by several signs like:

  • Swollen bellies
  • Pregnant females tend to move slower
  • Aggression towards other tankmates
  • A dark triangular spot in the vicinity
  • The tendency to eat more than the other fish in the tank

2. Sleeping

Another common reason why your molly fish is lying at the bottom of the tank is that they could be sleeping. You might be surprised that fish sleep, but they actually do!

Molly fish usually sleep during the night, so if you see your fish lying at the bottom at night while the lights are off, there’s a good chance they are just catching some Zs.

Signs that your fish is just sleeping:

  • The fish will be upright and balanced
  • Its fins will be slowly moving
  • The mouth will stop moving altogether

3. Diseases

Unfortunately, one of the more serious reasons your molly fish might be lying at the bottom of the tank is due to molly fish diseases.

There are a few different diseases that could be the culprit, but the most common ones are swim bladder disease and Ich.

Swim Bladder Disease

The vital function of your fish’s swim bladder is to keep it balanced while it travels in the aquarium.

Swim bladder disease occurs when the function of the swim bladder is disrupted.

Overfeeding and constipation can cause organs in the molly fish to push against the swim bladder, hampering its functioning. This might also arise from bacterial and parasitic infections.

Molly fish with swim bladder disease can’t go swimming regularly. Some simply move up and down in the aquarium, while others swim erratically or stay at the bottom or top of the tank.

Ich Disease

Ich disease is one of the most widespread infections in aquarium fish. It is caused by a parasite that can attack your molly’s skin, gills, and fins.

The initial sign of ich is small white spots on your fish which then turn into larger lesions.

Mollies that have been infected with ich will be seen rubbing their bodies against hard surfaces. This is one of the reasons why your molly fish may spend so much time at the bottom.

4. Overcrowding

Despite being community fish,  mollies need their space. They are not the type of fish that does well when overcrowded.

If your tank is too small or overstocked, your molly fish may become stressed. This can lead it to stay at the bottom of the tank.

5. Overfeeding

Although it is important to give your molly fish the appropriate amount of food, overfeeding them can be just as harmful. Overfeeding your molly fish can cause problems such as:

  • Unhealthy growth
  • A rise in ammonia levels
  • A decrease in oxygen levels

All of these issues can lead to your molly fish laying at the bottom of the tank.

6. Poor Genetics

In some cases, the reason your molly fish is lying at the bottom of the tank is due to poor genetics.

Some molly fish are simply born with genetic abnormalities that make it difficult for them to swim. These fish typically don’t live very long.

7. Introducing New Fish to the Tank

Whenever you introduce new fish to the tank, there should always be an adjustment period.

Your molly fish is no exception. When you first add a new molly to the tank, it may spend some time at the bottom until it gets used to its new surroundings.

8. Loud Noise

An inappropriate environment can hurt your molly fish. If there is too much noise or activity around the tank, it can stress out your molly fish. This may cause it to spend more time hiding at the bottom of the tank.

9. Improper Water Quality

Poor water conditions can also lead to health problems in your molly fish.

If the water in your tank is not clean or of poor quality, it can lead to stress and disease. This may cause your molly fish to spend more time at the bottom of the tank.

The water conditions that are harmful to your molly fish include:

pH Levels

Wrong pH levels can cause gill and skin problems which make it difficult for your molly fish to breathe.


Toxins like ammonia, nitrates, and heavy metals can also be harmful to your molly fish.

Some symptoms of toxicity include:

  • Fish gasping for air
  • Fish laying at the bottom of the tank
  • Fish rubbing against objects

Water Temperature

When your tank’s water isn’t appropriate, it can be fatal to your fish. Water that is too cold or too hot can cause your molly fish to go into shock.

This may lead to your molly fish laying at the bottom the searching for someplace with a more comfortable temperature.

10. Improper Lighting

An irregular day/night lighting cycle can also lead to stress in your molly fish.

This is because when this cycle is disrupted, it can lead to sleep deprivation and a loss of appetite.

Consequently, your molly fish may spend more time at the bottom of the tank to rest.

How to Treat Molly Fish Lying at the Bottom?

As you can see, there are many reasons why your molly fish may be lying at the bottom of the tank.

So, there are a few things you can do to treat your molly fish:

1. Check the Water Quality

It is essential to check the water quality in your tank regularly.

You can use a water test kit to check the levels of ammonia, nitrites, and nitrates in your tank.

If the levels of these toxins are high, it can lead to stress and disease in your fish. So, you should do a water change to remove these toxins from the water.

You should also keep the temperature between 72 degrees F and 78 degrees F, and the pH between 6.7 and 8.5.

2. Provide Them with a Proper Diet

As mentioned before, overfeeding can be just as harmful as underfeeding your fish. So, you should only feed your molly fish the amount of food they can eat in 2 minutes.

You should also give them a variety of foods to make sure they are getting all the nutrients they need.

3. Introduce the New Fish Slowly

Whenever you add new fish to the tank, you should do it slowly. You should first put the new fish in a separate tank and allow them to acclimate to their new environment.

After a few days, you can slowly add them to the main tank. This will help your molly fish get used to their new surroundings and reduce stress levels.

4. Avoid Overcrowding

Overcrowding can be harmful to your molly fish. So, you should make sure there is enough space in the tank for all the fish.

A good rule of thumb is to have 1 gallon of water for every inch of fish. So, if you have a 10-gallon tank, you should only have 10 inches of fish.

5. Treat Diseases

Looking after your molly fish is not just about keeping the water quality high. It is also important to look out for signs of disease and treat them as soon as possible.

You should check your fish regularly for any signs of disease, such as white spots, red patches, or cloudy eyes.

If you notice any of these signs, you should take your fish to the vet and get them treated.

6. Avoid Noisy Environment

Since molly fish are very sensitive to noise, you should try to avoid putting them in a noisy environment. Make sure that the tank is not in a high-traffic area or near any loud appliances.

7. Get the Right Tankmates

Hostile tankmates are a typical source of stress for fish. If you don’t want your mollies to hide at the bottom, get rid of any other fish in the tank that keeps harassing them.

However, if that’s not an option, you can also relocate your molly fish to a different aquarium.

8. Use Your Lighting Properly

It is important to allow your molly fish to have a regular daily/night cycle. You can invest in lighting that can be automated.

By doing this, you won’t have to worry about stressing out your mollies by forgetting to turn their lights off at night. Regardless of your presence or absence, automatic lights will help maintain a healthy routine for your fish.

9. Provide a Lot of Hiding Places

Hiding places can boost a molly’s confidence and make them feel more secure in their environment.

You can provide them with hiding places by adding caves, plants, or other decorations to the tank.

Last Words

If your molly fish seem to be spending a lot of time at the bottom of their tank, they might be sick or the water conditions might not be right for them.

Therefore, you should try to find out the cause of the problem and take the necessary steps to fix it.

We hope this article was helpful and you were able to find a solution to your problem. Thanks for reading! If you have any questions, please leave them in the comments below.

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