A goldfish that is swimming sideways or upside down may be suffering from swim bladder disease. This condition, which is also called flipover, usually afflicts fancy goldfish, and apart from swimming upside down and sideways, the goldfish may also swim with its nose up or down. Among the causes of swim bladder disease include constipation due to overfeeding or by swim bladder damage inflicted by intestinal parasites.
Also known as the gas bladder, the swim bladder is an internal organ in fish that is filled with gas. It helps fish swim better by regulating their buoyancy. The organ helps them maintain or change their swimming depth level without using too much energy.
Fancy goldfish may also develop swim bladder disease due to poor water quality or poor food quality. The common treatments for this condition include putting the goldfish on a fast for a few days or by feeding it green peas. With these simple treatments, the buoyancy problems usually resolve in a week or so.
Swim bladder problems may also be genetic in some goldfish, in which case, fasting or feeding with green peas may not be enough to treat the disorder. Fish surgeons can perform procedures such as placing a stone in the swim bladder or by removing part of the swim bladder to correct the buoyancy problem of the goldfish.