Why is my Goldfish Eating His Poop? (With 4 Quick Solutions)

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Quite frequently, I notice bizarre phenomena in my tank. For example, there were days when I saw my goldfish eating their own poop. As the years passed by, I learned what it could indicate and which cases require your attention. Now, I am willing to share my experience with you.

Goldfish typically eat their own poop due to their inherited instincts. As scavengers, they eat everything that fits in their mouths, including feces. To prevent this, one has to clean the tank and vacuum the substrate regularly; a pristine tank will keep goldfish from nibbling on their poop.

As we move forward, I will show you what other reasons could encourage your goldfish to eat their poop. I will also share a few tricks to prevent this from happening, and in what cases it may indicate that your goldfish is constipated.

Why do Goldfish Eat Their Own Poop?

Poop is one of the most annoying aspects of an aquarium. Not only is it unappealing to look at, but it can corrupt your water, contributing towards the concentration of ammonia. The idea of goldfish eating their own poop might sound attractive to some aquarists.

But don’t assume that it gets you off the hook. You are still expected to clean your tank. You cannot expect your fish to do this for you. Where the actual habit of goldfish eating their own poop is concerned, this is what you should know:

Where poop is concerned, you have to keep three factors in mind:

  • Goldfish are scavenging bottom feeders.[1] For that reason, they spend a lot of time looking for things to eat at the bottom of the tank. They are always on the lookout for more food, even when they have been fed.
  • Goldfish produce a lot of waste.[2] That is why the size of their tank matters. They are messy creatures that eat and poop a lot. All that poop sinks to the bottom, where they spend a lot of time scavenging.
  • Like most fish, goldfish will eat anything small enough to fit in their mouths. And unfortunately, poop is small enough to fit in the mouth of the average goldfish. 

For those reasons, the chances of a goldfish eventually stumbling upon its own poop and eating it are relatively high. As was mentioned above, the goldfish will eventually spit the poop out. But that won’t stop the fish from mistaking more of its poop for food down the line.

Some people will argue that a goldfish only eats its poop when it hasn’t been fed. This reasoning makes sense. Goldfish will look for alternative sources of sustenance if you fail to feed them to their satisfaction.

However, a well-fed goldfish is just as likely to mistake poop for food in an aquarium. A good meal won’t stop a goldfish from scavenging. These creatures are insatiable. They look like they are always hungry, which is why some aquarists keep making the mistake of overfeeding them.[3]

Do Goldfish Digest Poop?

Yes and No. If you think your goldfish are eating their own poop, observe them closely. You will see your goldfish nibble at the poop. They might also take it in their mouths, but they won’t swallow it. In fact, they are more likely to spit it out soon after.[4]

Fish don’t have hands. They don’t have any means of handling items in the water to determine whether they are viable food items before eating them. Their mouths are the only tools available to them. 

They may take the poop in their mouths, but they won’t eat and digest it. If your goldfish did take something into its mouth without spitting it out, it could be that you’ve confused feces with food matter. Fish can identify what they have picked quite quickly.

Is it Normal For a Goldfish to Taste Its Poop?

No, it is not. Aquarium fish don’t eat fecal matter. Most experienced aquarists you consult will agree on this issue. Yes, fish like corydoras and plecos have diverse appetites. People use them to clean their tanks because they will eat everything from leftovers to dead plants. 

However, even these fish avoid poop. They typically search for food leftovers and sunk pellets. They do not usually eat other fish’ poop. And if corydoras and plecos don’t eat poop, you can safely conclude that it isn’t common practice for goldfish to do so either.

How to Treat Goldfish That Nibble on Poop?

A goldfish’s poop isn’t dangerous. Even if your goldfish were to eat its poop, it wouldn’t suffer any significant consequences. However, that wouldn’t help your tank either. Yes, the poop might be gone, but your troubles don’t end here. 

Most of the nitrogenous waste associated with poop passes through the fish’s gills to enter the tank. For that reason, if the idea of goldfish eating poop bothers you, the following steps will eliminate this issue:

1. Feeding Your Goldfish Adequately

A well-fed goldfish can still eat its own poop by accident. However, a well-fed goldfish won’t spend as much time scavenging at the bottom, and neither will it search for sustenance in the tank as enthusiastically.

The best way to keep your goldfish well-nourished is to provide him with a diversified diet (rather than relying on pellets). For that, I highly recommend checking the Tetra JumboKrill Freeze Dired Jumbo Shrimp (link to Amazon). That vitamin-enhanced food matter will keep your goldfish healthy. It also fits perfectly in their mouths. 

When you feed your tank, you should also provide the right amount of food. Please give your goldfish the amount the consume within two to three minutes. Less than that may end up with starved fish. On the other hand, overfeeding may force your goldfish to poop more frequently and contaminate your tank.

To make sure you don’t skip any meals and pour the right amounts each time, I highly recommend using an automatic feeder. I personally use the Eheim Automatic Feeding Unit (link to Amazon). You can set the time and the precise amounts with that device, which allows you to put your mind away from your aquarium.

2. Maintaining a Clean Tank

Do everything you can to keep your tank clean. Goldfish can’t eat their fecal matter if you already removed it. That will also prevent ammonia and other toxins from accumulating. Try to replace 15-20% of your tank’s water weekly.

I also recommend using powerheads, such as the AQUANEAT Aquarium Wavemaker (link to Amazon). Use them to aim for a sufficiently strong flow at the intake of the filter. With the right configuration, you can prevent the goldfish’s poop from sinking to the bottom. The flow will carry it to the filter. 

However, for some people, it is much easier to vacuum the gravel. That will eliminate most of your issues since leftovers and feces tend to accumulate within the substrate. It isn’t that difficult to create a poop-free zone in your tank by performing regular water changes. 

If your tank is too dirty, you may notice that your goldfish are opening and closing their mouths rapidly, as I’ve described in this article. You may also see that your fish blows bubbles, as I explained here. If any of those is your case, please read those articles. I included some practical steps that will improve your goldfish’s general state.

3. Avoiding Allegedly Poop Eaters

That was mentioned above but it is worth repeating. You cannot rely on other aquatic creatures to eat the poop in your goldfish tank. Corydoras and plecos don’t eat poop, and neither do snails and shrimp. 

Instead, it would be best to find other means of siphoning the waste out of the water. Since the fish currently live in an artificial, sealed environment, it is the aquarist’s job to take care of the waste. As was mentioned, vacuuming the substrate can do miracles. 

4. Let Things be as They Are

As was mentioned earlier, goldfish are allowed to eat their own poop. Since they are scavengers, they will consistently seek for food matter to put in their mouths. There is nothing wrong with it as long as the fish does that rarely.

Goldfish may also eat other fish’s poop, sometimes before it had the chance to sink to the substrate. You may even see that phenomenon in other fish, such as guppies and mollies. Mostly, fast swimmers that spend a lot of energy choose to do so. 

If your goldfish doesn’t seem bloated and its feces doesn’t hang from its back in a stringy form, I would suggest living the things as they are. Your fish is merely behaving as it should, and how its genetics and instincts direct him.

The Question of Filters

Some people think that their goldfish are eating their own poop because they have seen the fish doing so. But others have come to this conclusion simply because they cannot find any fecal matter in their goldfish tank. As such, they cannot help but assume that their goldfish ate the poop.

If you have encountered this scenario, you shouldn’t be so quick to jump to the same conclusion. If you can’t find poop in your aquarium, your filter probably removed it. That can quickly happen in tanks with a bare bottom since poop typically hides within the substrate.

Is it Normal for Goldfish to Have Long Poop?

It is not normal for goldfish to have long poop. Goldfish poop should be chunky and medium-short.[5] It should also be the same color as the food the fish eat. If the poop is long and thin, the goldfish are eating insufficient quantities, most likely due to stress-related factors.

However, If the poop is long and thick, the goldfish has been overfed and is probably constipated. In many cases, the fecal matter remains attached to the goldfish and trails behind the creature. Luckily, you may treat that by feeding your goldfish peeled peas. 

Those are relatively soft and are likely to lubricate your fish’s digestive system. Yet, make sure that you remove the peel (you can do that by submerging the peas in water beforehand). Otherwise, things may get even worse.

If your goldfish is constipated, it may also lie on its side at the bottom of the tank. If your fish behaves this way, I highly recommend checking that article I wrote. I showed what steps to take to solve it before the situation deteriorates.

If the poop is not only long and clear, but it has bubbles, the fish is probably reabsorbing eggs. That could happen after the female goldfish spawned unfertilized eggs to the water. Nevertheless, it is quite a rare scenario and probably not the case if the water conditions are ideal.


If you’ve noticed that your goldfish eat its own poop, you probably have no reason to worry. That happens because goldfish are scavengers, a type of fish that will consistently look for things to put in its mouth. 

It is worth noting that goldfish don’t actually digest their feces. Typically, they will spit out the food matter once they realize it won’t benefit them. It is quite rare for goldfish to swallow and digest their poop. However, if your tank is relatively dirty, poop may compromise your goldfish’s health in other ways. 

For example, as it rots, the feces releases ammonia, which could be toxic for fish. For that reason, I highly recommend performing regular water changes. I also advise you to vacuum your substrate since it tends to hold in debris and leftovers.


  1. https://www.aqueon.com/information/care-sheets/goldfish
  2. https://en.wikibooks.org/wiki/Animal_Care/Goldfish
  3. https://www.cuteness.com/article/goldfish-starving
  4. https://www.fishwise.co.nz/view-article/10-back-to-basics/107-the-truth-about-poop-what-fish-eat-it
  5. http://www.utahwatergardenclub.org/diagnosing-a-sick-fish.html