I purchased 2 percula clown fish from a local guy i met off local forum site. The one clown is very pretty and a fair size the other is very dull colored and not very nice looking and smaller, the bigger one seems to nip at him when he does the little fish i noticed twitches like he is being shocked he sometimes does this even when the other clown doesn't nip at him anyone heard of this should i be worried there both active and eat really well ever since i got them .