Wow poor lil fh. Im sure the size of the tank is the root of his problem.(if thats what he lives in) I really dont think you can fix him. Im no expert but I would suggest gettin the fh a larger volume of water to work with. WHats the water parameters? After nuking the tank the bb may have died off as well. I would stop treating him untill he has a larger home. Clean water with many waterchanges will do alot for your fish.