Do Fish Poop? | (Spoiler) Yep, they do it discreetly!

This reminds me of a poem I read a long time back.

Does a fish go pee

when it’s swimming in the sea?

The answer is simple. Yes, fish need to excrete waste materials and liquids. That means if you are planning on a fish tank, keep in mind that you will need to keep your aquarium poop free clean.

I agree that the fact that they do not seem to have any other opening than the mouth makes things a bit confusing.

But like every other living organism fish need to ingest food and give out their waste through an excretory system.

To clear your confusion, let’s take a closer look at the subject.

How Do Fish Poop?

Fish need to poop, even though they are more discreet about it than humans.

In fact, around 16 percent of the total carbon in the oceans is from fish poop and other excrements.

Fish have an alimentary canal consisting of the stomach and intestine. The digested food from the stomach passes through the intestine by peristaltic movements and local contractions. The undigested food, along with bacteria, mucus, bile pigments, etc. get passed out in the form of feces.

Other than that, fish excrete ammonia along with smaller quantities of urea. Many fish have a small pore at their rear end which acts as an opening for excretion. Some fish also excrete wastes like ammonia through their skin and the gills.

Like mammals, the excretory system of fish includes kidneys. Generally, the kidneys of freshwater fish are larger than that of saltwater fish as they need to handle more water.

Actually, freshwater fish absorb more water through their skin. So, the amount of water they excrete is also more. Saltwater fish pass out more concentrated urine.

Now the shape and size of the kidneys can vary depending on the type of the fish. A scarlet gem or a zebrafish will have small kidneys. Long fishes like eels will have elongated ones.

Also, the kidneys of fishes take more time to process the solid waste matter. That means having a lower frequency of peeing.

And yes, fish do poop in the water.

Frankly, I have never seen them visit anywhere else for that purpose. In fact, many aquarium owners have caught their fish in the middle of the act.

What Does Fish Poop Look Like?

Fish poop can be round in shape and often stringy. Generally, it’s short to medium in length. It has a solid consistency and settles at the bottom of the tank. The color of the poop will depend on the type of food that the fish are consuming.

For example, fish on a diet of flake food will excrete brown or dull red-colored poop.

Beyond that, the color of the poop can also help you to determine the health condition of the fish.

Dark red or white-colored poop might indicate constipation caused by overfeeding or some form of an infection.

Sometimes you may find the thread-like poop hanging out from the rectum of the fish. Note, if it doesn’t fall off after a few minutes, there might be a problem. If the excretory pore is inflamed, it can be a case of roundworms. Or else, the fish might be infected by flagellates or bacteria.

White or pale yellow poop can indicate parasitic infections or a poor diet.

And you may find it hard to believe, but another reason for it can be high levels of stress.

If you do not see any solid poop but the aquarium water has a brown tinge, the fish are probably suffering from diarrhea.

In short, if you see the color and consistency of the poop differing from the food you are feeding them, consult a veterinarian.

Do You Clean Fish Poop?

The aquarium is not a moving body of water but a small and enclosed environment. So, whether you use gravel or sand in your aquarium, always clean the fish poop from the bottom at regular intervals.

The frequency of cleaning will depend on the number of fish present, and the number of plants and scavengers in the aquarium. Some fish species, like plecos, oscars, and goldfish produce more waste.

However, cleaning the tank once every two weeks is necessary. If it’s overcrowded, weekly cleaning will be necessary. If you have high-quality pumps and filters in the aquarium, the frequency of aquarium vacuum cleaning will come down.

On the other hand, in a natural environment, fish excreta plays a vital role for the coral reefs and other life forms in the ocean. The fish excrement delivers vital nutrients like nitrogen and phosphorus to the corals. The biodiversity of the coral reef is dependent on fish urine and overfishing is a serious threat to the reefs.

Research is also suggesting that fish poop plays an important role in the complex marine ecosystem to uphold the process of carbon capture and storage in the ocean beds.

Frequently Asked Questions

Do fish poop and pee?

Yes, fish need to poop and pee in the water they live in. They have separate excretory systems that take care of these processes.

Do fish poop sand?

Not all fish poop sand. But a particular species like the bump head parrotfish poop sand. They eat dead coral among other things and the calcium carbonate in the coral is passed out as white sand. A single parrotfish can produce several hundred pounds of sand in a year.