Why Is My Danio Swimming Erratically: Causes and Treatments

Zebra danio fish are one of the more popular types of fish kept in aquariums. They are attractive to look at and are fairly easy to care for. However, they can be quite active and may swim around erratically.

If your zebra danio is swimming erratically, there could be several reasons. Some of the most common reasons for fish swimming erratically include stress, disease, and even poisoning due to poor water quality. In this post, we will discuss the reasons why your Danio might be swimming erratically and what you can do to help them.

What Does Swimming Erratically Look Like?

If your zebra danio is swimming erratically, they will often swim in large circles or loops. They may also jump out of the water or up and down repeatedly. If you see this type of behavior, it is important to take action right away so that you can figure out what’s causing the stress and fix the problem.

A specimen of Danio rerio – zebra fish – in the aquarium

What Are Signs and Symptoms of Swimming Erratically?

If your fish is swimming erratically, there are a few things to watch for. Some of the signs and symptoms of a fish swimming erratically can include: swimming in circles, staying close to the surface of the water, and not making any progress. If you notice any of these signs and symptoms, it’s important to take your fish to a veterinarian as soon as possible.

If your fish is swimming erratically, it could be a sign of several issues. If the fish is gasping for air, it may be experiencing a respiratory emergency. If the fish is swimming in circles or making erratic movements, it may be experiencing some form of neurological disorder. If the fish is lethargic or not eating, it may be experiencing a medical condition. In any case, it is important to get your fish checked out by a veterinarian as soon as possible to rule out any serious issues.

Macro photo of a zebrafish (Danio rerio) with a black background.

What Causes Zebra Danios to Swim Erratically?

If you have a fish swimming around erratically, there could be a few reasons why. One possibility is that the fish is feeling sick and needs to get out of the water as quickly as possible. Another possibility is that the fish is feeling territorial and is trying to assert its dominance over its surroundings. Finally, a fish might be swimming erratically if it’s in danger or if it’s trying to escape from something.

Here are the most common reasons behind your fish swimming erratically:


If your fish is feeling stressed, it might start swimming around erratically to escape. If the stress is caused by something external (like a new person in the house), it may take some time for the fish to adapt and get used to its new environment. Once your fish starts swimming erratically, there’s not much you can do except wait it out and keep an eye on things.

Glass Surfing

One of the most common causes of fish swimming erratically is glass surfing. Fish are drawn to objects that emit light and movement, which is why glass can be so dangerous for them. If your fish sees or catches a glimpse of a shiny object, it might start swimming in circles around it. This behavior can quickly become addictive and ruin your water’s ecology as well as damage your fish’s health.

Ammonia Poisoning

If your fish is swimming erratically, it could be suffering from ammonia poisoning. Ammonia is a by-product of fish metabolism and can build up in the water if the fish aren’t getting the proper nutrients. This can cause the fish to swim in a frenzy to escape the toxicity and make them look sick. If you notice your fish swimming in a circle or making strange movements, it’s best to get it checked out by a vet. If the water quality is also poor, adding a filter will help to reduce the amount of ammonia in the water.

Poor Water Quality

If the water quality in your tank is poor, it can cause all sorts of problems for your fish. Constant drainage and poor filtration will allow harmful bacteria and chemicals to build up, making the water unusable for your fish. Not only will they become ill due to the pollution, but their swimming behavior may also change as they try to find a clean place to swim. If you suspect that your water quality is causing issues with swimming, get it cleaned up as quickly as you can. Good water quality is key for maintaining the health of your fish, and even small changes in behavior are better than nothing at all!

Swim Bladder Disease

Swim bladder disease is a condition in which the fish’s swim bladder becomes inflamed and swollen. This can cause the fish to lose its balance and start to swim in circles or tilt head over heels. If untreated, swim bladder disease can lead to death. One of the most common causes of swim bladder disease is an imbalance in your tank’s water chemistry. high levels of nitrates or phosphates will cause the organ to become inflamed. If you add a filter, try to keep the nitrate levels as low as possible and increase the filtration for your fish’s tank so that your water quality stays good.

Zebrafish Zebra Barb Danio rerio freshwater aquarium fish

How to Treat the Different Conditions That Cause Swimming Erratically?

Treating Swim Bladder Disease

If your fish is swimming erratically and exhibiting other signs of swim bladder disease and constipation, your veterinarian may prescribe a treatment to help relieve the fish’s symptoms. This may include administering laxatives or enemas or prescribing antibiotics to fight constipation. If the swim bladder is the source of the fish’s constipation, surgery may also be necessary to remove it.

Treating Bacterial Swim Bladder Disease

If your fish is swimming erratically, it may be due to a bacterial swim bladder infection. Treatment involves antibiotics and water changes. Parasites can also cause swim bladder disorder in fish, and treatment generally involves antibiotics to fight the infection. Depending on the type of parasite, additional treatments may be necessary, such as a diet change or medications.

Treating Bloating

If your fish is swimming erratically and exhibiting signs of bloating such as a swollen abdomen, it may be due to diet changes or other problems with its water quality. If the problem is caused by food, try switching your fish’s food to a diet that contains lower levels of fat. Cleaning and quarantine procedures can also help improve water quality in tanks infected with bacteria.

Treating Birth Deformation

If your fish is swimming erratically, it may be due to a birth deformity of the swim bladder. The swim bladder is a gas-filled organ that helps your fish control its buoyancy and moves water through the fish’s body. If the swim bladder is not functioning correctly, the fish may swim in an uncontrolled manner. If you notice your fish swimming in an erratic manner, it is best to bring it to a veterinarian for further examination.

Treating Physical Damage or Injury

If your fish is swimming erratically, it may be injured and in need of medical attention. Swimming in an erratic pattern could indicate that the fish is in physical pain and needs to be treated as soon as possible. Fish can suffer from several injuries, including broken bones, internal bleeding, and parasites. If you notice any physical damage or injury to your fish, take it to a veterinarian as soon as possible for proper care.

Treating Poor Aquarium Water Quality

If you have a fish that is swimming around erratically or not eating, the aquarium water quality is likely high in nitrates. Nitrates are a by-product of the nitrogen cycle and can build up in your aquarium if not monitored and corrected. A good way to test your water’s nitrate levels is to purchase a nitrate test kit and do a monthly check. If the nitrate levels are high, you will need to take steps to correct the problem.