HomeFreshwater FishFreshwater Aquarium BasicsWhy Is My Fish Swimming in Circles: 7 Reasons

Why Is My Fish Swimming in Circles: 7 Reasons

It can be confusing when you’re looking at your fish tank and noticing that your fish are swimming in circles.

Why is my fish swimming weird?, you might ask. It could be a sign of something minor, like hunger or boredom, or a more severe issue, like a disease or injury.

If your fish is displaying this behavior, it’s important to take a closer look at the situation to figure out what might be causing it.

In this blog post, National Park Aquarium will discuss some of the most common causes of fish swimming in circles and what you can do to remedy the issues. So, if you’ve been noticing this strange behavior lately, keep reading!

Why Is My Fish Swimming In Circles

Why is My Fish Swimming in Circles
Fish Swimming in Circles

1. Your fish is hungry

If your fish is swimming in circles, one possibility is that it’s simply hungry. Like all animals, fish need food to survive, and if they’re not getting enough to eat, they may start acting differently.

If you notice your fish swimming in circles and exhibiting other signs of hunger, like decreased activity levels or loss of appetite, try to feed them.

2. They Swim in Circles Out of Boredom

Fish are intelligent and curious creatures, and without stimulation or enrichment in their environment, they can become bored and start exhibiting behaviors like this one as a way to entertain themselves.

If you notice your fish swimming in circles frequently, try adding some new toys or decorations to their tank to keep them engaged and active.

3. There Might Be Disease or Injury

In some cases, your fish’s swimming pattern may be a sign of an underlying health issue or injury. For example, if something is wrong with your fish’s swim bladder, they may have difficulty swimming in a straight line and end up swimming in circles instead.

If you notice your fish swimming in circles and exhibiting other signs of illness or injury, like lethargy, loss of appetite, or abnormal behavior, take them to a vet for an evaluation.

Whirling disease

It is a serious illness that can be fatal to fish, and it’s caused by a parasite that affects the swim bladder. Symptoms of the whirling disease include circling behavior, loss of appetite, and difficulty swimming.

Swim bladder disorder

If your fish is swimming in circles frequently, they may have a condition called swim bladder disorder. This disorder can affect any type of fish.

It is caused by an issue with the swim bladder, an organ that helps a fish stay upright and control its buoyancy.

Some common symptoms of this condition include swimming erratically, floating at the surface, or swimming in circles.

Parasitic infection

When the fish is subjected to infection caused by parasites, which often appear in a tank with dirty water, they feel itchy. Therefore, fish swim in a circle to release themselves from the irritation. Also, they tend to rub against decorations like rocks and plants in the tank to remove the parasites.

Ammonia poisoning

If your goldfish is swimming in circles, there might be too much nitrite or ammonia in the water, poisoning them. As you check your tank’s ammonia level and notice it reaching 0.2 mg and above, it’s super dangerous to your fish.

fish disease or injury
Fish disease or injury

4. Fish Swim in Circles for Fun

There are a few other potential reasons why your fish might be swimming in circles. One is that they’re trying to catch their tail!

5. They are Bullied by Others

Suppose you see your fish frantically swim in a circle. In that case, you might see if other fish or aquarium lives are bullying it, especially the bigger fish.

They might be trying to escape from something, like a predator or another fish that’s bothering them. You can separate the fish or add more plants and decorations for the fish to have hiding places.

6. It’s The Fish’s Mating Ritual

Swimming in circles for some types of fish is the dance to attract their mates for breeding.

If you see your betta fish, especially male ones swimming to make circles, that’s their tactic to attract the female’s attention.


Fish swimming in circles is a common phenomenon. Some experts believe that the movement helps fish survey their surroundings and find food. Meanwhile, others think the circling may be a way to socialize or signal dominance.

Whatever the reason, it’s fascinating to watch these creatures navigate their aquatic worlds. Have you ever seen your fish swim in circles? What did you think was causing the behavior?

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Further Reading
Kevin Mills, the founder of Nationalparkaquarium.org


-- Founder --

I'm Kevin Mills, the founder of Nationalparkaquarium.org, where I share my deep passion for aquariums and aquatic life. With over 20 years of experience in fishkeeping, covering everything from tending to saltwater and freshwater tanks.

Kathleen Wood


-- Interrogator --

Kathleen Wood, a seasoned marine biologist, possesses a wealth of knowledge and experience in her field. Her research on tropical fish biodiversity spans over three decades, and she has contributed numerous scientific papers on aquatic life.