Goldfish looks dead and is lying at the bottom of the fishtank, but on looking again he is breathing as his mouth is opening and shutting. Put food in to feed him and he tried to move up but just couldn't. Is he on his way out? Should I put it out of its misery and just bury him alive and say to the children that he died or is this too cruel? children keep checking and are quite calm actually, already seen goldfish 1 die and be burried. thankss