I had 3 different times with 3 different fish with ICK. I had a Yellow Tang, a Volitan Lionfish(had it worst of all), and a Purple tang. They all had it pretty bad. 1 of the times (Lionfish) I scooped him out, did a 10min Freshwater Dip(RODI), then fed with Garlic in food. I bought a UV 18w for 55g, Feed LOTS AND LOTS of greend to the Tangs, and the Lionfish had LOTS AND LOTS of silversides. This overcame the ICK and I havent seen it for Ages since!