Does your pet fish have trouble swimming? If your fish floats on the surface or has a difficult time rising from the bottom, he has a buoyancy problem. The Japanese named this syndrome "tenpuku” disease, which means "capsized."
Not withstanding this, most fish given good husbandry & attention will thrive & be a constant pleasure to those of us, who like to replicate a small piece of nature in our own homes.
Buoyancy Problem
Diseases in Tropical Fish