Why Is My Angelfish Swimming Sideways?

The most likely cause of your angelfish swimming sideways is an issue with the swim bladder or swim bladder disease. This illness eventually prevents the fish from being able to swim properly. Other causes of sideways swimming in an angelfish could be gastrointestinal parasites or bacterial infections.

If left unaddressed, your angelfish’s sideways swimming issues could cause lasting damage to the fish. If swim bladder disease is left untreated, the fish cannot breathe or eat, easily resulting in death for the fish. Thankfully, swim bladder disease can easily be treated, and it can also be prevented quite easily.

Sideways Swimming, Explained

The most likely cause of sideways swimming in an angelfish is swim bladder disease. This progressive disease can result from various causes and can ultimately prevent the fish from being able to swim properly.

Because the swim bladder controls the fish’s buoyancy, swim bladder disease prevents them from maintaining buoyancy and causes them to float upside down or on their side.

If swim bladder disease is left untreated, it can result in breathing and eating problems, ultimately killing the fish.

Swim bladder disease in angelfish can be caused by many factors, including improper tank parameters, resulting in constipation and other issues.

Other Signs Of Swim Bladder Disease

Besides swimming sideways, there are other signs to look out for to determine whether your angelfish has swim bladder disease. While the erratic sideways swimming is a sure sign that there is some issue with the swim bladder, other behavioral factors might indicate the same issue.

If the swim bladder has swollen to a larger-than-normal size, the fish will be seen to spend most of its time floating along the top of the tank. The angelfish will likely sink lower in the tank if the fish has an undersized swim bladder.

Another sign of swim bladder disease is if the fish has difficulty eating. They may suffer a lack of appetite due to discomfort.

If the swim bladder issues have resulted in a distended stomach, the fish will have a noticeably curved back. Another sign to look out for is clamped fins. This is a major indication of declining overall health.

Involuntary shaking is another common occurrence with an angelfish suffering from swim bladder disease. This type of shaking may not be overly noticeable at first.

However, if you observe the fish closely while they swim, you may notice a slight shudder in the overall movement of the fish.

Silver blue angelfish isolated on black background

Causes Of Swim Bladder Disease

There are various potential causes of swim bladder disease. The four main causes of swim bladder disease amongst angelfish are incorrect tank conditions, inherent birth defects, parasites or bacterial infections, or simply overfeeding the fish.

Regarding tank conditions, various undesirable tank conditions could cause a swim bladder infection. To begin with, dirty water is a major potential contributor to swim bladder disease. If the tank water is dirty, the angelfish may internalize the bacteria or disease in the water.

The incorrect water temperature also plays a major role in swim bladder disease. For example, if the water is too cold, the angelfish’s digestion is affected to a large extent.

Severe impaction can result, and this can cause significant pressure on the swim bladder, eventually resulting in swim bladder disease.

Another aspect of tank conditions that can result in swim bladder disease is incorrect pH and incorrect nitrates.

Birth defects within the angelfish can significantly contribute to swim bladder disease. These birth defects can be present on the swim bladder itself, or they can be present on other organs.

Irrespective of which organ suffers a birth defect, the result can be pressure on the swim bladder, ultimately resulting in swim bladder disease.

Suppose the fish has suffered an injury from swimming into an object in its tank. In that case, it is possible that any swelling can cause damage to the swim bladder. The same goes for situations where the angelfish has gotten into a fight with another fish.

Any issues with the organs surrounding the swim bladder can potentially pressure the swim bladder, ultimately causing swim bladder disease.

Overfeeding is another common cause of swim bladder disease, so this should be avoided at all costs. Because freeze-dried food expands in water, Angelfish should also not be given too much of this type of food.

Preventing Swim Bladder Disease

While swim bladder disease can be treated, it’s naturally better to prevent it than treat it. Firstly, the most important factor is ensuring that the tank’s water remains clean at all times.

Regular water changes and testing of water parameters come with ensuring the water is clean.

The temperature of the tank water should also be kept constant. Angelfish enjoy warm water kept between 78 and 84 degrees Fahrenheit.

The food given to your angelfish daily must be high quality, nutritious, and balanced. If feeding dried food, this must be soaked for a few minutes before feeding. If the food is frozen, this must be thoroughly thawed before it is fed to the fish.

Avoid overfeeding your angelfish at all costs. Smaller, more frequent meals are generally better than a few larger meals in one day.

Role Of The Swim Bladder

The swim bladder plays an important role in the day-to-day functioning of the fish.

The swim bladder is essentially an organ filled with gas and air. This organ allows the fish to float at specific depths in the water without the need to actively swim.

This allows the fish to conserve energy overall. At the same time, the angelfish can enjoy moments of low activity or rest whenever required.

Because the swim bladder allows the fish to remain completely still when required, they can remain camouflaged to some degree when hiding from predators.

The fish can control buoyancy by increasing or decreasing the amount of gas in the swim bladder.


In most cases, an angelfish swimming sideways indicates that they are having an issue with their swim bladder. The health of the swim bladder is essential to ensure the angelfish can effectively maintain buoyancy. Swim bladder disease can be prevented and cured, provided measures are taken soon enough.