Why Is My Fish Swimming in Circles? Let’s Read To Explore!

Why is my fish swimming in circles? When it comes to this topic, many fish keepers and aquarists believe it is a normal and harmless thing.

It is true that sometimes fish swim in circles simply because they like it, but not in all cases. In some cases, the answer is more complicated than you think!

Why Is My Fish Swimming in Circles

If one day you find out that your fish are swimming in circles, it could be due to one of the reasons below.

  • For Fun
  • Stressed
  • Swim Bladder Disorder
  • Ammonia Poisoning
  • Whirling Disease
  • Mating Ritual

For Fun

happy fish

Your fish may sometimes swim in the circle for fun

Fish, like other animals, can be playful. So your fish may sometimes swim in a circle for fun. Of course, you won’t need to do anything in this case.

If your fish are kept in one round-shaped aquarium, such as a round fishbowl, they can swim around in circles to imitate the round surface of your tank.

It should be considered a normal behavior and nothing to worry about.


Improper Water Conditions

Improper water conditions can stress your aquarium fish.

It can be improper temperature, high nitrite/ammonia levels, low oxygen levels, and improper pH levels.

If you keep one saltwater aquarium, improper salt levels can also hurt your fish.

In this case, you must regularly maintain and change your aquarium’s water to ensure everything is right for your fish.

Improper Diet

feeding fish

An improper diet can also lead to stress in your fish

An improper diet can also lead to stress in fish. So consult a specialist or search online to determine the proper diet for your fish.

Other Fish

Your aquarium is too crowded or includes the wrong tank mate which can also cause your fish stress.

They can often be aggressive and fight over food and territory in these cases.

In this case, you should move some of the fish to another aquarium and ensure the fish in the same tank can get along.

In addition, you should also live plants or decorations to create hiding spots for smaller individuals.


If your fish is sick and struggling with an illness, you can add helpful medication that helps treat the specific disease.

Remember that medications can alter the specific aspects of your tank’s water chemistry. So whenever you treat your fish, you should start by quarantining it.

Swim Bladder Disorder

A swim bladder is a specialized internal fish organ filled with gas.

Swim bladder disorder refers to the fact that your fish’s swim bladder organ does not function properly because of some factors, such as diseases, mechanical, physical abnormalities, or environmental factors.

Once this situation occurs, your fish will show issues related to buoyancy, making it difficult to control its sinking and floating ability.

Here are some things you need to do once you notice this situation:

  • Let your fish fast for around three days.
  • Increase the water temperature to about 78 to 80°F and keep this condition during treatment.
  • When the fourth day arrives, feed your fish with skin removed and cooked peas. Keep this pea diet for several days.

After that, you can switch to a specific diet for your fish. Avoid floating flakes or pellets.

Ammonia Poisoning

Ammonia poisoning can also be a cause. It happens when nitrite and ammonia form in your aquarium.

Ammonia is a by-product of the fish waste and rotting fish food in your aquarium. The following are some of the leading causes of ammonia poisoning.

  • Add too many fish at one time in one established tank.
  • Filter failure because of mechanical or power failure.
  • Death of bacterial colonies because of using medications.

Here are some common signs of ammonia poisoning:

  • Lethargy
  • Appetite loss
  • Purple or red gills
  • Gasping for breath
  • Laying at the bottom part of your tank
  • Bloody patches on the body

Hence, it is essential to check the ammonia levels in the aquarium regularly.

Whirling Disease

If your fish swim in a very erratic way and a circular motion, chances are your fish are suffering from whirling disease.

The myxozoan parasite Myxobolus Cerebralis is the main culprit causing this disease.

This parasite can enter the fish’s body parts, such as the spinal cartilage and head. Then, it will quickly multiply before putting pressure on your fish’s organ of equilibrium.

Here are some common symptoms of this disease:

  • Darkened Tail
  • Twisted Spine
  • Deformed Head

Note that these symptoms are not always present. It is usually only confirmed by the microscopic slides.

Your fish may die from this disease. Sadly, there is no cure for this disease yet.

Mating Ritual

mating behavior

Some fish swim in circles around their mate during mating season

Some species swim in a circle around their potential mate during mating season.

It is a typical mating behavior often utilized to charm the potential mate’s attention.

The male betta is one of the great examples of this mating behavior. This fish features beautiful, long fins.

This species will show off its fins by swimming in a circle around one potential mate.


Are Fish Swimming in Circles Dying?

In some cases, swimming in circles can signal that your fish are struggling with disease, which can make your fish sick if not treated promptly.

Why Is My Fish Swimming Fast, Back, and Forth?

If your fish feel too cold, their activity increases, and you will see your fish swimming fast back and forth.

Why Is My Goldfish Swimming in Circles?

Swimming in circles, particularly in a jerky and darting motion, typically means your goldfish has ammonia poisoning.

What Are the Symptoms of Ammonia Poisoning?

If your fish is affected by this disease, it will show some physical changes with swimming difficulties. Most of the time, your affected fish will float at the top or sink to the bottom of your aquarium.

How Is Ammonia Produced in Aquariums?

Ammonia is formed from the metabolism of protein and is the primary waste product of your fish.


There are many reasons for your fish swims in circles. In many cases, it can be your fish’s normal behavior, but it is sometimes a sign of something that can become serious if not treated promptly.

So regularly checks the aquarium’s condition, the fish’s nutrition, and more to ensure everything is okay. Please share our article if you found it helpful!

Thank you for reading!