Swim bladder
The swim bladder is a gas filled sack inside most fish that controls their buoyancy in the water. Problems with the swim bladder cause the fish difficulty in swimming, and are common with fantail goldfish. Bacteria infections and air swallowing are thought to be common causes of these problems. Feeding a varied diet can help in prevention.
Swim bladder problems are not usually life threatening, however it can be a symptom of a more serious disease. If a fish is suffering badly for more than a day or two it can be worth using a swim bladder medication.
Some fish suffer regular bouts of problems; the fish is uncomfortable but soon recovers. If, however, a fish constantly suffers with swim bladder problems to the extent that it affects quality of life, you may wish to consider seeking advice from a vet.
