Name of disease: Swim Bladder Disorder
Other names: SBD, Floating Disorder
Type of disease: Physical Deformity / Bacterial / Feeding Problems
Occurrence: Common, especially in fancy goldfish, but can affect all freshwater fish.
Symptoms include: Fish cannot keep a normal upright position in water; it may list to one side, float upside down, swim pointing head-downwards or upwards, be unable to rise from bottom, be unable to swim down to bottom. Fish may become listless and stop eating, but many carry on eating as usual.
Caused by: The swim bladder is an air-filled organ which the fish uses to balance itself and swim up and down by regulating the pressure inside. If the airbladder becomes compressed, deformed or diseased the fish cannot regulate it and therefore 'loses its balance'. Fancy goldfish frequently suffer with SB problems due to their compressed body shapes; the cause may therefore be internal physical deformity. Other causes are constipation - which compresses the SB - gulping air whilst feeding at the surface or eating food with too much air inside, such as dry floating foods, Fatty Liver Disease or kidney cysts. Bacterial or internal parasitcial infections can also be involved, and egg impaction in female fish is an occasional cause. *See EDIT below.
Treatment: Initially, fast the fish for 2 - 3 days and then feed peas, lightly boiled/steamed, de-skinned and mushed (this is a cure for constipation). If this is not effective, increase the tank temperature to approx. 78-80F and add Epsom Salts - an eighth of a teaspoon per 5 gallons. If this is not effective, treat with a medicated food or a broad-spectrum antibiotic (suggestions are Medigold or MetroMed or Maracyn 1 and 2 in US, Myxazin in UK). If this is not effective, treat with an internal parasiticidal medication. If this is not effective, ask a vet to X-ray the fish to check if the swim bladder or surrounding organs are physically deformed or if the swim bladder is over-inflated; sometimes this can be surgically corrected.
For fish which are sitting on the bottom, it helps to reduce the water level in the tank to about half to lessen the water pressure on the fish. For fish floating at the surface, reduce the filter current if the fish is being swept around helplessly and put in plants which reach to the surface to provide the fish with some areas of gentle support. If the fish's tummy or back is constantly sticking out of the surface and is exposed to the air, coat the area with a light layer of Vaseline (petroleum jelly) to avoid it drying out and becoming sore.
Please note that sometimes it is not possible to cure chronic SBD. If the fish is obviously distressed and is completely unable or unwilling to eat then painless euthanasia might be the kindest thing for it. Most fish will deal quite well with mild SBD for long periods of time however; even completely upside-down fish usually cope for a while.
Precautions: Salt and medications affect the cycle so monitoring water quality during treatment is essential, especially if the tank volume has been reduced to half. Hand-feeding may be necessary as SBD-afflicted fish often cannot feed for themselves. Tank-mates may harrass a sick fish; if so then remove it to a hospital tank. Even after a fish has been cured of a bout of SBD, the disorder can return at any time so always pre-soak dry foods, use sinking rather than floating foods and keep the tank temp in the high 70's. Note: if tank temp is above 76F, ensure plenty of oxygenation is supplied.
*EDIT: Recent research has closely linked high nitrate levels with SBD; in many cases, 'floaty' fish were restored to normality fairly quickly when placed in nitrate-free water. It is therefore recommended to check the nitrate levels in tanks with fish suffering from SBD, and try to keep the nitrate level below 20ppm, max., at all times.