Close this search box.

Exploring the Characteristics of Fish Waste: Get the Facts

What Does Fish Poop Look Like?

If you own an aquarium or two, or even just stuck around pet stores watching a goldfish swim around in glee, you have surely caught them in the middle of pooping.

While the act itself is entirely normal, we’re bound to question if the long, stringy poops hanging out of them are.

I have owned many fish during my time, and I’ve seen a variety of fish poop that left me confused and even concerned. From green to brown, and from to pink, to white, it left me questioning. What does fish poop look like, exactly? What’s normal, and what’s not?

What Does Fish Poop Normally Look Like?

It’s widely acknowledged that fish are opportunistic eaters; they won’t hesitate to consume any available food, regardless of its form. I once witnessed my supposedly peaceful Glassfish feasting on the remains of one of my other small fish!

However, like all living creatures, the more fish eat, the more waste their tiny bodies produce.

Author Note: There are many debates as to what “normal” fish poop should look like. The general consensus is that it should look about the same color of the food they consume.

Fish fed with flake food usually expel red or brown poop. Fish fed with meat and/or shrimp expel pink poop. If they have had peas or types of algae, it’s green.

Normal fish poop has a solid consistency and will immediately fall to the bottom of the tank when expelled. Length-wise, it’s typically short to medium, not longer than half the fish’s body.

Identifying Disease Using a Fish’s Poop

goldfish eating

One of the best ways to detect internal illnesses is by looking at a fish’s poop. Similar to human beings, a poop’s color and consistency say a lot about one’s health. 

In the following section, I’ll be listing all the different types of fish poop appearances, including its colors and consistency. Let’s dive right in!

Long, Slimy, Stringy Poop

It’s common to find fish with poop hanging out of their anus. However, it’ll typically fall off after a minute or two. If the poop hangs longer than several minutes, this means that your fish is unable to expel it completely.

In this scenario, there are three possible reasons for long, slimy, stringy poop, no matter the color: 


The easiest way to check if your fish has roundworms is to, and I know this sounds a bit weird, check his vent or anal area. If it’s inflamed, there’s a possibility that he has roundworms.


If the anal area isn’t inflamed, flagellates may be the answer. Flagellates is a term used to coin a number of different flagellate parasites that are found in the intestinal tract of fish. They often cause mild infections. Nonetheless, they could be deadly if left untreated.


Bacterial infections are said to be the second-most common diseases aquarium fish experience, just after parasites. They’re often caused by either abrasions or physical injury, but can be brought on by poor diet and exposure to unsanitary water as well.

Flagellates and bacterial infections are often treated with DoxycyclineMetronidazole, or Paracide-D. Roundworms can be treated by Paracide-D. And although fish live in the same water they poop in, there’s no way they could survive in a toilet.

Pom-Pom Poop

If you noticed more than one string of poop hanging out of your fish, especially if it’s red or brown in color, the fish might be affected by Camallanus worms that bear live larvae. In such cases, it’s best to consult a veterinarian for medication.

Long, Thin Poop

Long, thin poop of any color could be an indication that your fish isn’t eating well. The loss of appetite in fish is commonly related to water conditions, possible infections, and/or bad food. Or maybe your fish is simply bored of eating the same food every day!

Although less common, it could also be a sign of a tumor or gut blockage.

Thick, Long Fish Poop

Fish that have thick, long poop are quite possibly constipated. Overfeeding is one of the major causes of constipation.

Because fish eat practically anything given to them, owners might be tempted to feed them more than twice a day because they believe they’re hungry.

Author Note: Chronic constipation in fish is a serious thing. It makes fish feel lethargic and disinterested in food. They may also find it difficult to swim normally.

To avoid constipation, it’s best to fish your fish no more than once or twice a day. Only feed fish as much as they can within 2-3 minutes. If they finish their food in less than 2 minutes, you can add a little more.

No Poop, But Water Is Tinged Brown

This might be a sign of diarrhea. Diarrhea in fish is often caused by bad food, bacterial, or viral infections.

White Fish Poop

There are many reasons why a fish’s poop is white in color. Many believe it’s a sign of disease or parasites. While this isn’t entirely untrue, there may be other explanations behind it.


Feces that are distinctively pale in color and slimy in appearance is a sign that your fish isn’t eating well. As Jessie Sanders, Doctor of Veterinary Medicine, simply states, “White stringy poop is a poop with no food in it.”

She also states that white, almost transparent poop isn’t actually poop, but mucus coating that fish expels. In other words, an empty fecal cast. Changing a fish’s diet helps, but if it persists, there might be something wrong internally.


Lumpy and/or white (and sometimes yellow) stringy poop could be a sign of parasitic infections, internal infections, or even high levels of stress. 

Parasitic Infections

The most notorious cause of white poop is Hexamitatapeworms, and roundworms. These parasites often come from the introduction of new plants, fish, and other objects inside the aquarium.

The good news is, though, parasitic infections in fish aren’t as common as you may think. Unless your fish has been caught in the wild, the chance of them having parasites is quite low.

Internal Bacterial Infections

Bacterial infections such as bloated stomach, swim bladder, and dropsy are some other causes for white, stringy feces. Oftentimes, these infections can be cured by fish antibiotics.

Bad/Poor Diet

Low-quality or bad diets may cause a fish’s poop to suddenly change from healthy brown to white. If a fish’s diet consists of too much fiber and fat, white segmented feces can be a result.

How to Properly Feed Aquarium Fish

fish in tank

In order to properly take care of your fish, you first need to know what your fish breed typically eats outside aquariums. Identify their natural classification: are they herbivores, omnivores, or carnivores?

Let’s break these classes down individually:

Herbivorous Fish

Herbivorous fish do well when fed flake food and algae wafers. To avoid constipation, it’s best to supplement your fish’s diet with freshly sliced veggies such as lettuce, cucumber, spinach, and green peas.

Examples of herbivore fish are:

  • Plecos
  • African cichlids
  • Pacus
  • Silver dollars
  • Livebearers

Omnivorous Fish

Most aquarium fish are omnivores, which means you can let them eat meat, plants, or both. Omnivorous fish are quite flexible in their food choices. Nonetheless, it’s best to keep them on a varied diet.

Examples of omnivorous fish are:

  • Goldfish
  • Mollies
  • Catfish
  • Angelfish
  • Barbs
  • Danios/Minnows
  • Gouramis
  • Rainbowfish

Carnivorous Fish

Not a lot of aquarium fish are carnivores. Those that enjoy eating worms, be it live or freeze-dried, meat, and frozen brine shrimp. Some fish, like the Oscar, prefer feeding on small, live fish.

Carcasses, or carrion, fall under this type of diet as well.

Examples of carnivorous fish are:

  • Jack Dempsey
  • Bettas
  • Oscars
  • Tetras

Recommended Food Quantity

fish food

It’s always best to underfeed fish. As stated above, overfeeding your fish may cause multiple health issues including constipation, bloating, and lethargy. Uneaten food can cloud your water as well, which in turn causes a dangerous rise in ammonia and nitrite in your tank.

Author Note: Remember, only feed your fish what they can consume within 2-3 minutes. If they’ve finished everything under 2, give them a little more.

Here are some tips to follow when feeding your fish:

  1. Make sure the food you’re feeding your fish is no larger than their mouth.
  2. Remove any food that remains in your tank with a net after five minutes, to ensure your water is always clean.
  3. Although fish can be fed anything, it’s best if you feed your fish in the early morning and at dusk. This will allow your fish to get used to your feeding schedule and anticipate their next meal.
  4. Don’t feed your fish more than twice a day. If you feed them more than this, they won’t be able to eat all of the food and it will begin to decompose in the tank. This could kill your fish.


“What does fish poop look like?” is a question many fish owners have asked themselves at least once.

Fish poop, just like any other type of poop, varies in color and consistency.

Normal fish poop should match the color of the food you are feeding your fish. It should come in one solid color and have a solid consistency. You should also pay attention to your fish’s scales. If they change color or begin to fall off, you might also want to consult with a veterinarian.

If you believe there is something wrong with your fish because of how their poop looks, it is best to visit a vet so they can prescribe you the right medication. You never know, you might not even need any medication at all! Maybe a change in diet will suffice.

We hope you found this article useful and informative.

Happy Hunting!


2 thoughts on “Exploring the Characteristics of Fish Waste: Get the Facts”

  1. Carlos Nelson

    I never thought about fish poop until I stumbled upon this article. It’s fascinating to learn about their waste and how it can indicate their health. Thanks for the interesting read!

  2. Alan Peterson

    This article on fish poop is truly fascinating! As an aquarium enthusiast, I’ve often wondered about the different types of fecal matter that fish produce and what they signify. The detailed explanations and insights provided in this article have shed light on the subject and answered my questions. It’s reassuring to learn what constitutes normal fish poop and what may indicate potential health concerns. Thank you for sharing this informative piece that has deepened my understanding of my aquatic pets. Keep up the great work!

Leave a Comment

Your email address will not be published. Required fields are marked *

Related Posts