actually, in many states it is illegal to release fish that have been kept in an aquarium, even if you caught them yourself earlier. the chemicals used for pet fish specifically say 'not for use on food fish', which a channel cat could end up as if it was caught. also, if you keep any other fish with it, they bring in parasites and bacteria which do not belong in the wild. even if your domestic fish don't get sick, wild ones could be susceptible.