Do fish pee and poop?

Whenever I come back home, my betta swims near the tank edges and asks for food. I love this site, and without wasting a second, I feed her some fish food pellets. But the thing that annoys me is that my betta doesn’t finish its food and I always find some pellets on the bottom of the tank or near the plants. But sometimes I keenly observe. I just toss two to three pallets that it eats happily. And then, after a few hours or within a day, I find the pellets again! I asked my friend about it and guess what he told me? It’s not the food that is sitting near plants and on the bottom of my fish tank. Then what is it?

So, I asked some experts and did my own research as well. Here’s the crisp of it:

Do fish pee and poop? Yes, fish pee and poop. Fish need to excrete the waste material, but the process is rather slow. You need to clean the tank every day because the pee and poop can infect your fish and contaminate the tank.

Do fish pee and poop? (Video)

Do fish pee?

Yes, fish excrete liquid waste as urine. The fish in your tank, the one in the pond, fish in freshwater, marine fish, and every other fish found anywhere, pees.

Fish have two kidneys, just like us. The size and shape vary according to the type of fish. Eel fish have long kidneys, while some fish have shorter kidneys. The kidneys filter out waste material and excess water.

Although fish don’t require peeing after every two hours (unlike us) but they do pee daily. The kidneys of the fish process much slower, and that is why the excretion rate is low.

I know you must be wondering how they pee? Where’s the opening, and is an opening necessary for the excretion of liquid or not?

Let’s find out now.

How fish pee?

Most of the fishes have an opening just around the tail, and that is from where they pee. But the opening is not necessary. Fish can excrete through their gills and skin, as well.

The gills can filter out the waste and excrete it. Fish’s skin is permeable, and that is why they can use their skin to pass out waste products.

But nature has developed their excretory system on the basis of their habitat. The place where fish lives count a lot and fish have evolved according to their habitats. The type of water in which fish lives decides the type of secretions. The waste of freshwater fish is much different from that of marine fish. And that is why their excretory systems work in different ways.

Freshwater fish:

Freshwater fish need to excrete an excessive amount of water and retain the salts. That is how their body will function normally. An optimum amount of salts is required for their proper growth and development.

Freshwater fish can’t afford to lose many salts. That’s why their kidneys allow the water to pass out of the body while the salts remain in the body. Only a small amount of salts is excreted.

The pee of freshwater fish is watery and not very smelly. Freshwater fish pee a lot as their intake of water is more, as it’s more water and less salts.

Most freshwater fish have a proper opening in the posterior part of the body through which they pee.

Saltwater fish:

Marine fish live in a salty environment, and they don’t need too much salt in their bodies. That’s why their kidneys are designed to pass out salts and retain water.

Their pee consists of salts with some water. Marine fish’s pee is concentrated and not very watery. That is because of too many salts in it.

Marine fish don’t pee a lot. They usually pee after every one or two days.

Marine fish mostly use their gills and skin to excrete the waste. Some also have an opening near the tail for peeing purposes.

How often fish pee?

The liquid intake of fish is very frequent. But that liquid (water) also comes out through gills. The excess is excreted in the form of pee.

Fish don’t pee a lot. They just need to pee once in a day. But it’s also not necessary. It depends on the environment and food.

Freshwater fish pee is more watery than marine fish. Also, if the metabolic rate is high, the fish will pee more frequently.

Is fish pee good for other aquatic creatures?

Here’s a kicker: Fish pee is very nutritious for some sea creatures.

Although it seems disgusting, but actually, it’s not. The pee of fish contains several nutrients, and these nutrients are food to many sea creatures.

Some plants, algae, and animals extract nutrients from fish pee, and they remain around fish so that they don’t miss a drop.

Coral reefs:

Corals are marine invertebrates, and they develop a hard, rocky house for them- the coral reef.

Corals literally look for fish pee. Many fish live inside the coral reef as it’s a safe place to hide from predators. Fish easily find food there. When they pee, the tentacles of corals absorb the pee and extract important nutrients for their optimum growth and development. They extract potassium and calcium from the pee.

The corals can’t survive without fish pee. That’s why nature has made the coral reef home to many fishes, and thus the process goes on smoothly.


Sea anemones are colorful, flowery predator animals. They need fish pee for proper growth. They also extract nutrients in the fish pee.

But this process happens with the help of algae. Let’s see how.


Sea anemones are home to algae. It happily accommodates algae in it, and both provide mutual benefits to one another. Sea anemone provides shelter, and algae provides it with food.

The algae that live on sea anemone absorb fish pee and convert it into sugar. This sugar is consumed by sea anemones to get energy.

So, this is how the fish pee is really beneficial for many aquatic plants and animals.

How to know if your fish is peeing in the fish tank?

Now that it’s established that all fish pee, how to know if your fish in the aquarium are peeing? Well, just smell the ammonia in your fish tank in case you don’t change the water regularly. This ammonia smell is due to fish’s pee.

Fish pee contains a small amount of ammonia, as well. When all the fishes pee and you don’t change the water for two to three days, then it stinks.

Can you notice from the color of the water? Well, no. Mostly the pee is the same colored as of water or slightly different. So, you can’t tell that your fish are peeing by just seeing the color of the water.

Health problems when your fish isn’t peeing:

When the fish is peeing regularly, then it means its kidneys are functioning normally. But if you notice that your fish isn’t peeing (when there is not much ammonia smell even when you don’t change the water), then it means that there’s some kidney or excretory system problem.

The fish might get stone or other hard substances in the kidney, and due to this, the kidneys might not be able to work properly. Also, it might happen that the fish isn’t taking its diet, or the water intake is very less.

In case your fish isn’t peeing, then there’s some underlying problem. You can consult a vet who’d examine your fish. This underlying problem also causes other problems like kidney infections.

Kidney infections and their impact:

It might happen that some parasite infestation results in kidney failure and/or other urinary tract problems.

Due to infections, the fish might suffer from:

  • Renal dropsy: It occurs when a parasite named Sphaerospora auratus infects the kidney. The kidneys fail, and abdomen swells due to the accumulation of waste material inside it. Renal dropsy usually affects Goldfish.
  • Carp dropsy: It occurs because of the infestation of a parasite called Sphaerospora angulata that also fails the kidney. The abdomen and eyes swell in this case. It occurs with mostly carp species.
  • Proliferative kidney disease: It affects young fish that are grown commercially, particularly commercially grown trout and salmon.

In all the cases, unfortunately, fish don’t survive much. They become extremely sluggish and die within six months of the disease.

Do fish poop?

Yes, fish poops. All the fishes in all the habitats poop. But the nature of poop differs according to the habitat and food they consume.

As fish poop, it means their large intestine works well. They have a relatively developed digestive system as compared to insects and invertebrates.

The frequency of poop is much low. Fish usually poop after a minimum of 48 hours. The poop process is also very slow because of slow digestion.

What’s the color of fish poop?

The color of fish poop totally depends on the diet of fish. Those fish who are fed pellets of fish food, often poop red. That’s because of the blood worms in the pellets.

Some fish poop green, and that’s because their diet consists of plants and peas. If you feed your fish one or two peas, it will poop green.

The poop of hungry fish would be anywhere between white to brown.

What’s the nature of fish poop?

If you find pellets near the plants or bottom of the tank, then it’s most probably poop and not uneaten food pellets. Some fish like betta poop in the form of hard pellets. They like to poop in a private area, and that is easy to clean as you’ll know where they’ll poop.

Some fish poop stringy and sticky as well. If you find strings inside your tank, it’s time to clean your tank.

Some fish also poop sand! Do you want to know more? Read the “related questions” part for it.

Do fish constipate?

Yes, fish can suffer from constipation. It happens when they eat hard or too much food. Their digestive system can’t process hard food, and it takes a lot of time. As a result, the waste material gets hard, and the fish can’t poop.

You’ll know your fish is constipated when it’ll not eat food and swim lazily. Also, when there’d be no pellets and strings in the tank, you’ll get to know that your fish is constipated.

Steps to be taken if your fish is constipated:

If your fish is suffering from constipation, then you can try the following steps to ease it.

  • Offer peas: Peas are rich in fiber, and fibers help to soften the waste material. You can give one to two peas, and your fish will poop within 24 hours.
  • Offer fibrous food: If you don’t have peas, feed it with other fish-friendly fibrous food.
  • Take to the vet: If you feel like the fish isn’t pooping even after eating peas and other fibrous foods, then call a vet and get it checked.

Poop accumulated in the body due to constipation is not good for your fish as it can convert into poison and can be deadly.

How to clean your fish tank from fish pee and poop?

Your fish pees and poops. So, you have to clean the fish tank regularly.

What if you don’t clean the water? The fish can get infected as their poop contains poisonous waste substances. It’s vital for your fish’s health to keep the tank clean.

Change the water:

What you can do is to change the water regularly. Turn off all the filters and air pumps, and change almost 10% of the water on a daily basis.

Change 50% of water weekly. In this way, the water remains clean as the debris is washed away.

When you’re introducing tap water, boil it first to remove chlorine as chlorine isn’t good for fish. Also, place your fish in a separate small tank with that water and check if it’s suitable for it.

Lastly, don’t forget to clean the outer surface of your tank as many germs can crawl from outside of the tank and infect the water.

Use algae scrapper:

Use a scraper to clean debris from plants and ornaments. It’s very important to remove waste from them as it can infect the water.

So as a responsible fish keeper, you have to clean your fish tank regularly for the health of your fish.

Related Questions

Do fish have a bladder?

Yes, fish have a swim bladder that helps them to maintain their buoyancy. They don’t have a bladder as we do in their urinary tract.

Do fish drink water?

Yes, fish need water for proper functioning. Saltwater fish drink lots of water as the maximum of it is excreted due to excessive salts.

Are white sand beaches made of fish poop?

Believe it or not, some islands and all-white beaches are more or less made of fish poop.

A Parrotfish- named so because of its Parrot-like beak- eats corals and coral reefs also. It has sharp teeth through which it can bite the coral reef. Parrotfish also have pharyngeal teeth through which they can chew the hard coral reef. When their food is processed, the coral reef comes out as a waste product in the form of white sand.

A single Parrotfish can produce tons of white sand per year. And most of the coral reefs near beaches are inhabited by these Parrotfish.

Leave a Comment