How to Treat Gas Bubble Disease in Freshwater Fish

Air supersaturation in water leads to fish getting the "bends."

Goldfish bubbles


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 occurs due to the water becoming supersaturated with dissolved gas, and often causes the water to contain very small bubbles, known as microbubbles, that slowly form larger, more visible bubbles. The dissolved gas is absorbed by the fish and forms bubbles in its tissues. There are several ways microbubbles may occur in 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 eye, fins or skin. They may also be present within the internal organs. The gas is most commonly nitrogen and may be a collection of small bubbles or may coalesce into larger bubbles. Carbon dioxide and oxygen bubbles are also 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. This can be due to tiny microbubbles held in suspension, but cloudy water can also occur from algae, bacterial blooms or suspended debris. The tiny bubbles in the water are similar to those that occur when a glass of water is poured too quickly out of a faucet, or the bubbles that appear in a glass of champagne. To test if the water cloudiness is from microbubbles, collect a sample of the cloudy water in a glass and allow it to rest undisturbed for 30-45 minutes. If it is from suspended particles in the water, you will notice a film of sediment 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 pond or aquarium that has a potential gas bubble disease episode. If the fish has bubbles visible in the skin or fin, an aspirate using a syringe with a fine needle will be performed to see if the bubble is actually air or a clear fluid.

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

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

Causes of Gas Bubble Disease

There are many causes that may introduce microbubbles into your fish pond or aquarium. The most common cause in home aquariums is a cracked or barely disjointed pipe or filtration component. A pinprick hole allows for tiny air bubbles to get sucked in by 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. If you turn off the pump for the filtration system, you may find water leaking out from a pipe or the pump, which is where the air has been getting into the water, as water moving under high pressure may actually suck the air in, rather than pushing the water out.

Another place where bubbles can be introduced is at the bottom of a tall water fall or feature. The most common occurrence in an aquarium is when water is not filled to the top. The impact of the water from the waterfall mixing with the lower water can introduce bubbles of various sizes. The bubbles may cause supersaturation of gas in the water, 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 aquarium that is significantly warmer or cooler than your current water temperature. Unless you are intentionally trying to manipulate the temperature of your aquarium, 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 adjust your tank or pond temperature, go slowly in order to not stress your fish with sudden temperature changes more than a few degrees.

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 aquarium 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.

In ponds that have abundant algae growth, or in aquariums with many plants and high intensity lighting, the algae and plants will produce oxygen by photosynthesis, and can actually supersaturate the water with oxygen. Tiny bubbles will be seen on the plant leaves or algae strands. If the water temperature is warm, supersaturation followed by gas bubble disease can occur.

Treatment of Gas Bubble Disease

The most important treatment of gas bubble disease is to determine the cause of the microbubbles within the pond or aquarium. 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 aquarium or pond 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.

Once the source of the supersaturation of gas in the water is determined and corrected, the microbubbles will naturally disperse with time. Gentle stirring of the water will help degas the water. Lowering the water temperature slightly will also help, as cooler water holds more dissolved gas naturally, but don't cool more than a few degrees at a time.

Fish that get gas bubbles trapped in their body are similar to SCUBA divers getting the bends. If the supersaturation of the water is eliminated, the gasses will naturally disperse out of the fish and the bubble will go away. However, before that happens, if the bubbles get in the fish's brain, heart, kidney or other organs, the disease can be fatal before it resolves. Fish that get bubbles in their fin capillaries may lose fin tissue, even when the superstation is corrected, due to blocking blood flow to the fins.

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 pond or aquarium.

  • Make sure all plumbing and filtration components are properly connected and sealed.
  • Keep your water level at an appropriate height and top off as necessary. Keep track of your water change schedule so you will be able to notice leaks early.
  • Always check the temperature of your water when adding more during water changes, and keep the the temperature the same or within a few degrees.
  • Monitor the water for microbubbles, like seen in champagne. There should never be an abundance of bubble forming on the aquarium glass or décor items, or on the sides of ponds.