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Do Molly Fish Eat Their Own Poop? ( Surprising Answer! )

Fish poop is something that every aquarist hates because it can cause water quality issues. There is a lot of debate over whether molly fish eat their own poop and why do they eat poop.

While it will be cool to have a poop-free aquarium, you can not have such an aquarium as mollies poop a lot, although they might eat some.

In this article, we will talk over the reasons why do molly fish eat their own poop and, if they do, whether or not it is dangerous for the fish.

Do Molly Fish Eat Their Own Poop

Do molly fish eat their own poop?

Molly fish eat their own poop on rare occasions.

Some people claim that mollies eat their own poop because they are designed to do so in their natural environment.

But, if your molly is eating poop, it indicates a problem with your molly, your feeding schedule, or the water quality in your aquarium.

What do mollies eat?

Mollies are omnivorous fish, and they eat a wide range of food items. In the wild, mollies will eat smaller fish and insects as well as plant matter.

If you want to keep mollies in an aquarium, you should give them algae-based flake food and dried or frozen live food like bloodworms.

You can also feed your mollies live or frozen brine shrimp and daphnia. You can even give them pellets but do not use them as the only food source.

It is important to note that mollies are fish that can eat plants in an aquarium. The natural diet of mollies is moving from tiny insects to larger plants.

Pellets, flakes, and bloodworms are excellent high-protein food sources, but mollies also need plant sources as well. In addition to plants, they need to eat plenty of vegetables and fruit. 

Mollies have a voracious appetite and will accept any kind of food that you give them. Some owners complain that their mollies eat fish food quicker than they can dump it into the tank.

This means that if you overfeed your mollies, they will eat more food than they need, and their waste can pollute the tank.

Do mollies poop a lot?

Yes. As mentioned before, mollies are voracious eaters that eat each and every food they find in the aquarium. This causes them to poop a lot, causing water quality issues.

So, it is important to control your feeding to keep the water quality clean. Further, overfeeding causes health issues with the mollies.

Is it normal for fish to eat their own poop?

For scavenger fish like plecostomus or catfishes, eating their own poop is normal behavior.

But, mollies are not scavenger fish. They may nip at algae and debris to find some food, but it is not natural for them to eat their own poop. So, if you see any molly eating their own poop, it is time to observe and find the cause.

Reasons for molly fish to eat their own poop and how to prevent it

Mollies eat their own poop for several reasons.


When your fish are underfed, they will turn to anything available to find food.

This might include their own poop at some point. While it is not usual for mollies to eat their own poop, they may eat if they don’t get enough nutrition (food) from their surroundings.

How to prevent it

If you think your fish are eating poop because of this reason, you will have to increase the feeding amount.

The ideal feeding amount is an amount that your mollies can eat within 3 to 5 minutes. If your mollies finish eating their food as soon as you feed them, it means that you are not feeding them enough.

In this case, simply feed more than you are currently feeding, and your mollies will eventually stop eating their own poop.

Internal parasites

If fish has internal parasites, it causes them to have malnutrition even though you feed them enough.

When fish have internal parasites, they may show other signs and symptoms other than eating their own poop. The main sign that your fish is infected with parasites is that your fish will look very thin and lose a lot of weight.

How to prevent it

If you think your fish might have internal parasites, you will need to go to the veterinarian. The vet will test your fish and determine if your fish has parasites.

Once you know that your fish has internal parasites, you will need to deworm them for about three weeks with the help of your vet.


Some fish pick on their own poop out of curiosity.

As mollies are voracious eaters, they try to eat everything they find around them. This includes their own poop. However, a healthy fish will never eat poop and spit out any poop if they pick on them.

How to prevent it

You will have to clean the tank more often to prevent this. As mollies eat a lot, they produce more waste, which causes water quality issues if left uncleaned. Clean the tank every 5-7 days for best results when you have a fish that eats a lot.

Water quality issues

When your aquarium water is not clean enough, your fish will turn to any source of food available, including their own poop.

This is especially the case if your mollies have some issues due to poor water quality. Fish usually eat their own poop to eliminate any leftover food in their digestive system.

How to prevent it

Your fish might eat their own poop due to water quality issues. Before you even stop it, you need to solve the root cause. If you clean the tank every 5-7 days and use water conditioners, you shouldn’t have any problem with water quality issues.

Molly fish poop colors

Observing molly fish poop color can help you identify any problem with your fish.

Healthy molly fish poop is dark in color, almost black. If your mollies eat their own poop, the poop will look lighter in color.

If your molly fish are eating their own poop due to water quality issues or poor nutrition, the poop will look much lighter in color than their regular poop.

If your molly fish are eating their own poop due to parasites, the poop will look white or creamy and will be stringy.

So, if you observe stringy white or creamy poop that floats if not eaten by your molly, you should immediately treat your fish for parasites. A dewormer will work for this condition.

Molly fish poop color may change to reddish, pinkish, brownish, or greenish depending on what they eat. But, these colors are nothing to worry about as they also indicate a healthy fish.

Aquarium fish that eat poop

Although it is not normal for mollies to eat their poop, some aquarium fish eat their own poop.

For example, scavenger fish like plecos and catfish eat their own poop while searching for food. It is not clear whether they spit the poop out or not, but many have seen these fish eat their own poop.

Recently asked questions

Does fish poop dissolve?

Yes. Most fish poops dissolve into the substrate of the fish tank as it is an organic matter.

This poop goes through the aquarium’s Nitrogen cycle, where it is broken down into basic elements that fish can absorb.

What breaks down fish waste?

Good bacteria break down fish waste in your fish tank. The good bacteria (or Nitrifying bacteria) eat the poop first, and the poop can be completely gone over time.

Does fish poop float or sink?

The poop of a healthy fish should always sink. If your fish’s poop is floating, it means that your fish has an illness, stress, or a poor diet.

Usually, fish poop floats when fish suffer from Ich, constipation, or internal parasites. So, check for signs and symptoms and treat your fish to solve this problem.

Do you have to clean fish poop?

Although fish poop dissolves and goes through the Nitrogen cycle, some residue can be left that can harm your fish. Therefore, it is essential to clean fish poop at least bi-weekly to keep the tank clean.

How often should I clean fish poop?

You should clean your tank every week or at least bi-weekly to keep the tank clean. You must vacuum fish poop while changing water; otherwise, it can harm your fish.


In general, mollies eat their own poop if they don’t get enough nutrition because of malnutrition, internal parasites, or water quality issues.

If your fish are just curious about their poop, you can simply clean the tank more often to prevent this.

If you see your molly fish eating their own poop, know that it is not usual. First, perform a water change and clean the tank.

If this continues for long, you can assume that your fish has a parasite issue. Treat your fish for parasites to prevent your molly fish from eating their own poop.

Credit to : Aquarium Genius
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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.