What happens if a fish has too much air in it?

Fish don't "have air" in them. If a fish is bloated or if it keeps floating towards the surface of the water it may have swim bladder problems or it may have a bacterial infection and it will probably die. This kind of problem is usually caused by bad water care ie. poor filtration and insufficient water changes. . The basic rules for sucessfull fishkeeping are. 1 inch of fish needs at least 1 gallon of water. :- Every tank must have a permanently running cycled filter. Every tank needs at least 50% of its water replaced every week.