I have a yellow tang and for the first couple weeks I had him if I even looked at him funny he would get ich.I tried a couple of things but the one that worked over night! was Called NO ICH this stuff is amazing. I have a reef tank so this stuff is completely safe and won't harm inverts and has no copper! I would try this immediately! oh and if you have a bunch of snails just do half treatments that's what I did and I have been ich free ever since! good luck.