Depends on the type and size of the fish and who is in the tank who might eat the dead fish. Small fish with very little bone mass can almost disappear, leaving only a small slime. Fry for instance. Large fish like Oscars may bloat and float to the surface while being picked apart. Catfish may crawl into a hole in a rock and stay there while you have the rock out for tank work so that you only find them when you put the rock back. There is no firm way to say what you may find. Often dead fish will float around until they are sucked up against the filter intake leading people to believe that the filter killed them.