Inability to swim upright in a regular fashion. Often appears to “float” from the section where the tail joins the body. Struggles to maintain equilibrium.
If the fish is constipated, cease feeding it dry fish food flakes and replace with another food, such as frozen blood worms. Also, don’t feed the fish too much and make sure the aquarium has ample supply of live aquarium plants. Many goldfish are predominately vegetarians so if there is a lack of plants this is an obvious cause for problems.
If the fish actually does have a deformity nothing much can be done to fix the problem. An operation to remove excess air is sometimes recommended. A fish can live up to a year with this problem, provided it is very well looked after and fed mainly plants and worms. Avoid dry pellets and flakes. This is very rare, however, compared to other causes.
Keeping the temperature stable and avoid fluctuations in water temp or conditions will also help swim bladder problems.
Remember, water quality is always extremely important- so always check that first as it is often the cause of disease in aquarium fish. When treating sick fish, try to put the least amount of stress on them as possible, as stress will hinder the heeling process. Another thing is to remember is that generally, a healthy fish is a happy fish.