Aqua Care

Gas Bubble Disease in Freshwater Fish

Gas Bubble Disease presents as bubbles trapped within a fish’s eye, fins or skin. It does not include any swim bladder or buoyancy disorders. This disease starts as a collection of very small bubbles, known as microbubbles, that slowly form larger, more visible bubbles. There are many ways microbubbles may be invading your aquarium. In order to successfully treat the disease, the origin of the microbubbles must be identified and eliminated.

What is Gas Bubble Disease?

Gas Bubble Disease occurs when gasses are supersaturated (dissolved beyond their normal limits) in the water, forming small bubbles that are visible within a fish’s eyes, fins, or skin. They may also be present within the internal organs. The gas is most commonly nitrogen and maybe a collection of small bubbles or may coalesce into one or two large bubbles. Carbon dioxide and oxygen bubbles are possible, but these gases are frequently used by fish tissues and readily processed.

Symptoms of Gas Bubble Disease in Freshwater Fish

Bubbles are visible within the anterior chamber behind the cornea of the eye. Bubbles within the skin may be visible as an external lump or felt by moving a hand along the fish. Bubbles can also be seen between the fin rays in the clear membrane of the fins. Internal bubbles are not visible and may cause tissue degeneration. It is very rare to have only internal bubbles without external bubbles.

You may notice your water clarity has become cloudy. These can be tiny microbubbles held in suspension. It is similar to a glass of water poured too quickly out of a faucet. To test your clarity for bubbles, collect a sample of the cloudy water and allow it to rest undisturbed for 30-45 minutes. If it is sediment in the water, you will notice a film on the bottom of the glass. If it is microbubbles, the water will become clear, and there may be bubbles adhered to the inside of the glass, like in champagne.

Diagnosis of Gas Bubble Disease

Most cases of gas bubble disease can be diagnosed upon a physical exam. It is critical to assess all animals within a system that has a potential gas bubble disease episode. An aspirate will be performed to see if the bubble is actually air or clear fluid.

In order to determine if there are any internal bubbles, an x-ray or radiograph may be taken of your fish. This procedure usually requires sedation in order to get a good picture.

Gas bubbles may also be present within gill tissue. This can be seen on a wet mount of the gills, a common aquatic diagnostic procedure.

Causes of Gas Bubble Disease

There are many causes that may introduce microbubbles into your fish system. The most common cause in home aquariums is a barely disjointed pipe or filtration component. A pinprick hole allows for tiny air bubbles to get sucked in through the movement of the water through the filtration system. Check your pumps and filter equipment to be sure no air is getting into the pump and is being pressurized and blown into the aquarium. There should not be high volumes of bubbles pumped into the water from your filter.

Another place where bubbles can be introduced is at the bottom of a tall waterfall or feature. The most common occurrence is a fish tank that is not filled to the top. The impact of the water from the waterfall mixing with the lower water can also introduce bubbles of various sizes. The bubbles may vary depending on your water temperature and bioload.

Sudden changes in water temperature can cause bubbles to form since the partial pressure of a gas changes with water temperature. This is most common when you add water to your system that is significantly warmer or cooler than your current water temperature. Unless you are intentionally trying to manipulate the temperature of your system, it is critical to always test your water temperature whenever you do water changes and try to match the new water to the current water temperature. If you are using your water changes to change your tank or pond temperature, go slowly in order to not stress out your fish.

Gas supersaturation in water occurs when the total pressure of gases within the water is higher than the surrounding atmospheric pressure. Depending on how your system is set up and the atmosphere within the room surrounding your aquarium, you may have microbubbles forming from simple atmospheric weather changes. If you have gas bubble disease without a clear cause, you may want to record the barometric pressure surrounding your tank for a few days and see how the gas bubble disease starts or dissipates.

Treatment of Gas Bubble Disease

The most important treatment of gas bubble disease is to determine the cause of the microbubbles within the system. It may not be as straightforward as you think!

Since there are many potential causes, it is critical to eliminate them in order to keep the disease from getting worse. Check the aeration, water pumps, water flow back into the aquarium and look for tiny bubbles on plants, décor, or the walls of your tank. Turning off the filtration temporarily and looking to see if bubbles are forming may help determine if the filter is the cause of the gas supersaturation. It is also important to evaluate all animals within the system to make sure that all those who are symptomatic are effectively treated. Your veterinarian will likely remove the bubbles by aspirating them with a very small needle and syringe. Antibiotic therapy is a common addition to any gas bubble disease treatment protocol. Barometric chambers have been employed in some cases if they are available to your aquatic practitioner.

Your veterinarian will likely remove the bubbles by aspirating them with a very small needle and syringe. Antibiotic therapy is a common addition to any gas bubble disease treatment protocol. Barometric chambers have been employed in some cases if they are available to your aquatic practitioner.

How to Prevent Gas Bubble Disease

In order to successfully prevent gas bubble disease, it is important to evaluate all the potential causes and eliminate them from your system.

  • Make sure all plumbing and filtration components are properly plumbed and sealed.
  • Keep your water level at an appropriate height and top off as necessary. Keep track of your topping off schedule so you will be able to notice leaks early.
  • Always check the temperature of your system and the new water you are adding during water changes.


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