Gas bubble disease refers to the development of gases in a fish's bloodstream. This can occur when its aquarium or pond water is supersaturated with gases.
Gas bubble disease damages the fish's tissue, causing tiny gas bubbles to form in the gills, fins, and eyes of the animal. This tissue damage, if extensive, can even lead to the fish's death.
Fishes are cold-blooded creatures, meaning their body temperature depends on the temperature of their environment. The water they live in and their bloodstreams can become supersaturated with gases when there is a sudden rise in water temperature or a sudden rise in pressure.
When the cold water in the aquarium is suddenly heated, it can release and trap gases within the water causing gas bubble disease in the aquarium fish. Similarly, pond or tank water can become supersaturated with gases when they are filled with well water through a submerged hose. These gases can also lead to gas bubble disease.
Gas bubble disease can be prevented by slowly heating up water when it is added to the aquarium. Also, do not submerge the hose when filling up a pond. Instead, spray water from above, as this will allow all the gases to harmlessly released into the air.