29 Gallon salt tank with water parameters within normal ranges across the board. 2 small ocelaris clowns and one fire fish. live rock, but no filter. introduced some snails and hermit crabs to clean algae and within a few days the clowns were getting white spots along the bod and fins. Today one of the clowns died, but the fire fish has had no signs of white sports at all, no where. have checked it several times daily and checked water parameters daily.. fire fish has no signs at all of any spots, not on fins or anything. it is moving and eating and acting normally. the other clown still has white spots on body and fins. several ove the snails and crabs have also died, but did not display any signs of being sick, no spots, no noticable actions that made me think they are unhealthy or acting weird. Snails/crabs died about a week after i got them and 3 days before the clown. I asked an employee at my local fish store for advice, they sold me a bottle of something called Ich attack.. it does not have copper and is save for inverts and corals.. dont have corals yet. also they said to turn up the temp to 84 F. So I dont understand.. why would the fire fish not appear to be sick? would there be any reason the clowns are stressed and got sick but not the fire fish? could the snails/crabs have introduced something that only affected the clowns? I am very confused, it doesnt make sense to me that some fish get sick and others dont.