Swim Bladder Problems in Goldfish

October 24, 2012

Goldfish come in all shapes and sizes. Most commonly found is the standard-type goldfish, those possessing a trim body shape, or alternatively, fancy ornamental varieties such as fantail, ryukin or oranda can be found. Those fancy-type fish are often bred to have large billowing fins and a shorter wider body shape. The fancy goldfish are more likely to develop swim bladder problems causing them to lie in an upside down position. Because of the shape of the fancy fish's body, an enlarged swim bladder can easily flip the goldfish upside down. Swim bladder problems lead to unwanted increased or decreased buoyancy.

A swim bladder is a thin-walled sac in the front of the fish abdomen that can expand or contract to help control buoyancy. The sac is attached to the esophagus (via the pneumocystic duct) in goldfish and the swim bladder is juxtaposed to a rich collection of blood vessels. The oxygen that comes in through the fish's gills is transferred into the sac from the blood vessels to inflate it. An inflated swim bladder increases buoyancy. This is because the increased fish volume is not associated with an increased weight. A deflated bladder decreases buoyancy, allowing the fish to dive deeper. The pneumocystic duct acts as a pipe that can vent excess gas from the swim bladder into the gut system quickly.

Causes of swim bladder problems are diverse and perhaps multi-factorial. Reported causes include:

  1. Bacterial or viral infection of the swim bladder that result in the lining of the bladder becoming thickened, thus interfering with the transfer of gas into the sac or reduced sac elasticity. This decreases the ability to change sac volume as needed.
  2. Species predisposition due to anatomical variation. Mentioned above, the globoid shape of many fancy fish predisposes to abnormal swim bladder function.
  3. Feeding regimens. Some report that fish take in excess air if they access their food on the surface of the tank. Evidence to support this etiology is sketchy. Others attribute problems to switching food sources from moisture rich gels or live food preparations to dried pellets and flakes. The lower fluid content and subsequent rapid expansion as water comes into the digestive system is thought to contribute to constipation, which can physically interfere with the ability of the swim bladder sac to expand within the abdomen or empty excess gas into the digestive tract.

Preventive measures may include gradual feed changes, pre-moistening dried foods, feeding live food or gels containing higher moisture content, keeping water and aquarium clean, and watching new additions (isolate new fish first) to help maintain disease-free aquarium status.

Treatment will be prescribed based on the specific condition of the fish, but if infection is confirmed, therapy may be prescribed. Some suggest feeding a few peas as a source of fibre to help relieve constipation if constipation is determined to be a contributing factor. Ask your veterinarian to assess your fish for you so that if a treatable condition is identified, proper therapy can begin.