Numerous conditions can cause bloating, including bacterial infection, egg-binding and constipation. When bloat is more severe, it can be fatal.
Bloat is usually a symptom of another problem in a fish. When fish are bloated they are larger than normal, especially around the abdomen or swim bladder. Sometimes, the fish can become so bloated that their scales get pushed outward giving the fish a bristly, pine cone appearance. When the condition gets this bad there is usually a lot of internal damage and recovery is unlikely.
When fish owners first notice bloat in their fish, remove the fish to a clean tank with water that is a couple of degrees warmer. Consider giving the fish some chopped, partially cooked peas as a constipation treatment. If constipation is the problem, owners should see results within 24 hours. Owners may also consider treating the water with a small amount of Epsom salts, which can encourage bowel movements.
If the scales are protruding from a bloated fish, the condition may be Dropsy, which is caused by the retention of fluids from a bacterial infection. This condition is often fatal, but owners may try treatment with antibacterials. If the fish is female and the bloated area is actually a protrusion, it may be egg-binding. The eggs are stuck inside the female fish. Without a veterinarian's intervention, the fish may also die.