Understanding and Overcoming Gas Bubble Disease in Fish

Gas bubble disease in fish occurs when water is supersaturated with dissolved gas, leading fish to absorb these gases and develop bubbles within their bodies. The excess gas absorbed by the fish forms microbubbles in its tissues, which can merge into larger bubbles and obstruct blood flow. Gas bubble disease in fish resembles the bends experienced by SCUBA divers. Successful treatment requires identifying and eliminating the source of excess dissolved gases. Here's what you need to know about gas bubble disease in fish and its treatment.

What is Gas Bubble Disease in Fish?

Gas bubble disease in fish is a condition where microbubbles develop within tissues and blood vessels due to gas supersaturation in the water. Bubbles may form in the fish's eyes, fins, skin, and internal organs. Microbubbles can merge into larger bubbles, potentially obstructing blood flow and causing illness, including fin and organ necrosis. Gas bubble disease differs from buoyancy disorders like swim bladder disease. Fish that get gas bubbles trapped in their body are similar to SCUBA divers getting decompression sickness, also known as ' the bends.'

Symptoms of Gas Bubble Disease in Freshwater Fish

Fish with gas bubble disease may show various signs:

• Disorientation or restlessness
• Swimming near the water's surface
• Visible bubbles in eyes, skin, or fins
• Protruding eye (one or both)
• Darkened skin
  

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

You may also notice that your aquarium water has become cloudy, with tiny bubbles on plants and aquarium walls. This cloudiness can be due to tiny microbubbles held in suspension, but cloudy water can also occur from algae growth, 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.

What Causes Gas Bubble Disease in Fish?

Gas bubble disease in fish is caused by the supersaturation of gasses in aquarium water, which are absorbed by fish and become trapped in the body. Supersaturation occurs when excess gasses are too much for the water to hold relative to the temperature, salinity, and atmospheric pressure.

Excess nitrogen is most often responsible for gas bubble disease in fish. Carbon dioxide and oxygen bubbles are also possible, but these gases are frequently used by fish tissues and readily processed.

Supersaturation can be caused by sudden changes in water temperature or pressure, sometimes due to equipment malfunction. Deep well water can have gasses under pressure that will be released if used in an aquarium without prior aeration, especially if the water is cold, and quickly warmed up.

Equipment Malfunction

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 push the water out.

Waterfall Features

Another place where bubbles can be introduced is at the bottom of a tall waterfall or fountain 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.

Water Changes

Sudden changes in water temperature can cause bubbles to form because the partial pressure of a gas changes with water temperature. This occurs most commonly when you add water to your aquarium that is significantly warmer or cooler than your current water temperature. Unless you are intentionally trying to adjust the temperature of your aquarium, it is critical to always test your water temperature when you make water changes and try to match the new water to the current water temperature. If you're using your water changes to adjust your tank or pond temperature, go slowly to avoid stress to fish with sudden temperature changes of more than a few degrees.

Weather

Gas supersaturation can occur 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, microbubbles may form from simple atmospheric weather changes. If your fish 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.

Algae Growth

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 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.

How Veterinarians Diagnose Gas Bubble Disease in Fish

Most cases of gas bubble disease can be diagnosed upon a physical examination. It is critical to assess all animals within a pond or aquarium that have a potential gas bubble disease episode. If the fish has bubbles visible in the skin or fins, an aspirate using a syringe with a fine needle will be performed to see if the bubble is air or a clear fluid.

To determine if there are any internal bubbles, an X-ray radiograph may be taken of your fish. This procedure usually requires sedation to calm the fish 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.

How to Treat Gas Bubble Disease in Fish

To treat gas bubble disease, 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.

To further treat gas bubble disease in fish, you must determine the cause of the microbubbles within the pond or aquarium. Since there are many potential causes, it's critical to eliminate them to keep the disease from getting worse.

• Check the aeration, water pumps, and water flow back into the aquarium.
• Look for tiny bubbles on plants, décor, or the walls of your tank.
• Turn off the filtration temporarily to see if bubbles are forming, which may mean the filter is the cause of the gas supersaturation.
• Evaluate all animals within the aquarium or pond to make sure that all those that are symptomatic are effectively treated.
  

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 remove excess gas from the water. Lowering the water temperature slightly will also help, as cooler water holds more dissolved gas naturally. Do not cool the water more than a few degrees at a time.

Prognosis for Fish with Gas Bubble Disease

If the supersaturation of the water is eliminated, the gasses will naturally disperse out of the fish and the bubbles will go away. However, if the bubbles have already formed 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. Early detection and treatment are key to fish survival and recovery.

How to Prevent Gas Bubble Disease

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 temperature the same or within a few degrees.
• Monitor the water for microbubbles, like those seen in champagne. There should never be an abundance of bubbles forming on the aquarium glass, décor items, or on the sides of ponds.