Swim Bladder Disease
Pathogen/Cause: Various; Often indigestion in goldfish and other "balloon" breed fish, but may be bacterial infection in other species. Occasionally, sudden trauma such as when fish are jostled excessively in transit or "dumped" into water without acclimatization may result in fatal injury to the swim bladder.
Physical Signs: May show some limited bloat, but usually no real physical changes.
Behavioral Signs: Fish has great swimming upright despite active attempts to do so. May occasionally float "belly up".
Potential Treatment: Different depending on species; goldfish are very susceptible and sometimes cured by discontinuation of diet and salt bath, followed by change in diet to high fiber digestible foods. However, other fish may require antibiotics and have a worse prognosis. Recently introduced fish that exhibited signs within a matter of minutes have the worst prognosis of all, and there is often no cure for trauma to the swim bladder.
Other Notes: Most common in "pot-belly" shaped breeds of fish, such as goldfish & parrot cichlids due to blockage and insufficient fiber/vegetable matter in the diet. However, many fish that suffer trauma or excess stress, or just get an internal bacterial infection that occurs on or around the swim bladder may have problems. Baby fish fry that have swim bladder problems are commonly known as "belly sliders" (most scoot around the bottom fo the tank, unable to swim up, or spin uncontrollably in the water). It is still unknown if this is the same exact disease entity or what the cause is, but most attribute it to congenital or developmental causes, sometimes birth defects, premature birth or inadequate nutrition at certain stages. They should be culled to prevent suffering.
