Swim Bladder Disease in Aquarium Fish

Causes, Treatment, and Prevention

goldfish in aquarium

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Swim bladder disease is a condition when the swim bladder isn't working properly because of various possible factors. A swim bladder is a gas-filled internal organ that helps bony fish maintain their buoyancy. The disorder refers to a collection of issues affecting the swim bladder, rather than a single disease. Although commonly seen in goldfish and bettas, swim bladder disease can affect virtually any species of fish. The disorder is often treatable, and a fish can experience a full recovery.

What Is Swim Bladder Disease?

Swim bladder disease refers to a condition when the swim bladder does not function normally because of disease, physical abnormalities, mechanical or environmental factors, or for reasons that cannot be diagnosed. Affected fish will exhibit problems with buoyancy, meaning they'll have difficulty controlling their ability to float or sink.

Symptoms of Swim Bladder Disease in Aquarium Fish

Sometimes a fish owner may think fish floating abnormally in the tank are dead, but they're actually exhibiting symptoms of swim bladder disease. Fish suffering from swim bladder disease exhibit a variety of symptoms that primarily involve buoyancy.


  • Sinking to the bottom of the tank (or floating by standing on its head at the bottom of the tank)
  • Floating to the top of the tank
  • Struggling to stay upright
  • Fish swimming upside down
  • Fish swimming sideways
  • Distended belly
  • Curved back
  • Changed appetite

Sinking or Floating to the Top

If the swim bladder is deflated, it will sink in the tank. If the fish has gulped in too much air while feeding, this may cause it to float to the top of the tank.

Struggling To Stay Upright, Swimming Upside Down or Sideways

A fish that does not have buoyancy problems tends to remain static and upright in the water. If your fish are struggling to stay upright—or swimming sideways or upside down—you will see excessive fin movement they're using to try to float the right way.

Distended Belly

Compression of the swim bladder may cause a the fish to swim with a distended stomach. The fish's digestive process may become disrupted with this disorder, which may cause the belly to become enlarged.

Curved Back

If the fish's abdomen is inflated, other organs are pushed aside which can sometimes cause the spine to curve.

Changed Appetite

Affected fish may eat normally or have no appetite at all. If severe buoyancy problems exist, the fish may not be able to feed normally or even reach the surface of the water.

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Causes of Swim Bladder Disease

This disorder can be caused by many issues, spanning from environment to feeding problems, including the following:

  • Rapidly eating, overeating, constipation, or gulping air may occur with floating foods to cause an extended belly and displace the swim bladder. Eating freeze-dried or dry flake food that expands when it becomes wet can also lead to an enlarged stomach or intestinal tract.
  • Other abdominal organs may become enlarged and affect the swim bladder. Cysts in the kidneys, fatty deposits in the liver, or egg binding in female fish can result in sufficient enlargement to affect the swim bladder.
  • Low water temperature can slow the digestive process, which in turn can result in gastrointestinal tract enlargement that puts pressure on the swim bladder.
  • Parasites or bacterial infections can inflame the swim bladder as well.
  • Occasionally a hard blow from striking an object in the tank, a fight, or fall can damage the swim bladder.
  • Rarely fish are born with birth defects that affect the swim bladder, but in these cases, symptoms are usually present at an early age.

Diagnosing Swim Bladder Disease in Aquarium Fish

Typically, swim bladder disease is diagnosed at home by the observation of symptoms. You can choose to bring your fish to a veterinarian specializing in aquatic conditions. If you do, the only way to properly diagnose swim bladder is with an X-ray. The X-ray will show the swim bladder's size, shape, and location. If there is any fluid or other abnormalities inside of the bladder. An X-ray can also show if there is another growth or disease that is pushing on or displacing the bladder.

To locate a fish veterinarian near you, contact the American Association of Fish Veterinarians.

Swim Bladder Disease Treatment

Treatment involves water maintenance, feeding changes, and possible antibiotics.

  • Let the fish fast: If an enlarged stomach or intestine is thought to be the cause of a swim bladder disease, the first course of action is to not feed the fish for three days.
  • Fix the water temperature: At the same time the fish is fasting, increase the water temperature to 78-80 degrees Fahrenheit and leave it there during treatment.
  • Feed the fish peas: On the fourth day, feed the fish a cooked and skinned pea. Frozen peas are ideal for this, as they can be microwaved or boiled for a few seconds to thaw them, resulting in the proper consistency (not too soft but not too firm). Remove the skin, and then serve the pea to the fish. You can continue to feed a pea a day for a few days and then switch to a species-appropriate food but avoid flakes or pellets that float.
  • Antibiotics: If an infection is thought to be the cause of a fish's swim bladder disease, treatment with a broad-spectrum antibiotic may help. For this, you'll need to visit your veterinarian.

Other supportive treatments (regardless of the cause) can include the following:

  • Keep the water especially clean and temperatures between 78 and 80 degrees Fahrenheit.
  • Add a small amount of aquarium salt to the tank.
  • Reduce the water level to make it easier for the fish to move around within the tank.
  • Reduce water flow in tanks with a strong current.
  • If the affected fish floats with part of its body constantly exposed to the air, applying a bit of Stress Coat water conditioner (which helps improve the fish's slime coat) can help avoid the development of sores and reddened spots.

Prognosis for Aquarium Fish With Swim Bladder Disease

Sometimes, a swim bladder disease is only a temporary condition that responds to treatment. Fish with this disorder will have a problem eating, which can be fatal, so you may need to hand-feed your fish if it has significant issues with movement. Unfortunately, many cases of swim bladder disease do not respond to any type of treatment. If the fish does not recover in a reasonable period of about one or two weeks of treatment, the humane resolution may be euthanasia.

How to Prevent Swim Bladder Disease

  • It is well known that poor water conditions cause fish to be more susceptible to infections. Keeping the tank clean and performing regular water changes can help prevent swim bladder disease.
  • Keeping the water temperature a bit higher will help digestion, and possibly avoid constipation.
  • Feed only high-quality foods, and consider soaking dried foods for a few minutes before feeding. Always thaw frozen foods thoroughly before placing them in the tank. For fish who gulp air when feeding at the surface, try switching to sinking foods.
  • Avoid over-feeding at all costs. Feed smaller portions so fish can’t overeat and watch the total amount you feed throughout the week.

Is Swim Bladder Disease Contagious to Other Fish?

A swim bladder disease is not contagious from fish to fish. However, it's best if you move your ill fish to a separate tank where they can be treated and observed. The tank should be empty of gravel or plants so you can clearly see how the fish are doing. Use fresh water, and do not use water from the tank from which the fish came because the water could have caused the problem.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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