Gas Bubble Disease in Fish

Gas bubble disease in fish, also known as supersaturation or “the bends,” can occur for a few different reasons and can affect both freshwater and saltwater fish.

It’s important to know the symptoms of gas bubble disease in your fish so you can seek treatment as quickly as possible. Although this disease is not fatal on its own, it can cause a lack of oxygen in the fish, causing distress that can result in secondary diseases and other issues.

What Is Gas Bubble Disease in Fish?

Gas bubble disease occurs when air bubbles become trapped in fish organs that do not typically involve air, such as the eyes or gills. These air bubbles impede the movement of blood, causing strictures in the blood vessels. This results in less blood and oxygen delivery to the various internal organs.

Gas bubble disease in fish must be treated quickly in order to preserve normal function of the fish’s affected organs.

Symptoms of Gas Bubble Disease in Fish

• Bulging or protruding eyes (one sided or both sides)

• Positive buoyancy (the fish floats unless they actively swim away from the surface)

• Lethargy

• Decreased appetite

• Visible bubbles in the fish’s eyes or skin

What Causes Gas Bubble Disease in Fish?

Gas bubble disease is caused when very small microbubbles, initially invisible to the human eye, diffuse into the fish’s blood through the gills. These very tiny bubbles collect in one space slowly over time until they are large enough to become noticeable to a pet parent.

If tank water becomes oversaturated with gas, the fish’s body absorbs the excess gas that forms bubbles within the tissue.

The most common space for gas bubble disease to visibly occur is within the eye of the fish.

The most common causes of gas bubble disease in fish include:

• A very small plumbing leak causing microbubbles to become incorporated into the system. This is typically seen with external hoses connected to canister filters and chillers. The hose attachment points are the most common sites for tiny leaks, and pinprick holes in tubing (especially in older tubing).

• Gas diffuses out of the blood stream during a sudden change of environmental pressure or temperature.

• Gas bubbles form in tissues after trauma, typically in eye-related injuries due to aggression from tank mates.

How Veterinarians Diagnose Gas Bubble Disease in Fish

Gas bubble disease can be diagnosed through a simple eye exam by a veterinarian. A veterinary ophthalmoscope or magnifying lens is typically used to evaluate the structures of the eye in all species.

Diagnostic Testing for Gas Bubble Disease in Fish

X-rays are typically taken to check for free air anywhere else in the body. Free air within the coelom, the main internal cavity in fish where their organs are located, is an emergency and needs to be treated as soon as possible to prevent organ damage.

Your fish will require sedation in order to remain still for an X-ray to be useful. A fish can be held inside their holding container, a bag of tank water, or without water and gently placed on the plate for a few seconds. Your veterinarian will determine the best technique for your fish.

Two images will be taken, one with the fish on their belly and another on their side. These two images can be combined to locate the precise location of the trapped air.

A CT scan may be prescribed if the equipment is available. A CT gives the veterinarian a much more detailed view of all the potential free air issues.

Gill biopsies may also be taken to evaluate the presence of gas bubbles within the gill tissue.

How To Treat Gas Bubble Disease in Fish

Minor GBD Treatment

Minor gas bubble disease may be resolved by adjusting the environmental issues at play (such as tank water pressure or temperature).

Be sure to monitor your fish for a few weeks to make sure they recover, confirming the environmental issues were the initial cause of disease. This may require a recheck assessment from your veterinarian to ensure the initial cause of gas bubble disease has been resolved.

Severe GBD Treatment

Severe gas bubble disease is typically treated by aspirating or lancing the free air by using a needle. Multiple aspirations may be required, depending on how long it takes for the gas bubbles to work their way out of the fish.

Medications

Administering antibiotics is also recommended to prevent secondary infections. Antibiotics may be given systemically, either by injection or orally, and/or as a topical treatment.

Topical treatments can be used to help heal the eye faster but wash away quickly when the fish is placed in water. Pet parents may be required to do treatments themselves at home, which will require some minor capture skills to decrease stress and not chase the fish too much.

Monitoring Environmental Factors

As with any disease, monitoring water quality and providing a high-quality diet are essential to proper healing.

In severe cases, the affected eye may need to be surgically removed. Depending on the species, your fish may require a prosthetic eye or implant.

Recovery and Management of Gas Bubble Disease in Fish

If microbubbles are noted in the gills or other tissues, it can take a few days to weeks for them to resolve, depending on the environmental conditions of the tank or pond. A veterinarian can aspirate large air bubbles from your fish, including those found internally on X-ray.

If gas bubble disease is left untreated, it can lead to loss of the eye or other internal tissues. Gills affected by gas bubble disease will not be able to diffuse oxygen as easily, leading to a buildup of carbon dioxide in the fish along with severe lethargy and respiratory distress.

Severe cases involving surgery may require that your fish be kept in a hospital tank for a period.

Fish with removed eyes typically do not have any issues eating food or swimming but will take some time to adjust to their new normal routine.

How To Prevent Gas Bubble Disease in Fish

• Check all plumbing and ensure tight seals.

• Ensure all fish are getting along and not overly aggressive.

• Closely monitor temperature fluctuations.

• Monitor atmospheric pressure.