well, this is my opinion, i have been taught that all fish have ich, its just getting it out of them is the problem, stress-poor water cond.- other fish with present ich on them, ect. i had purhcased a blue hippo tang which i later learned is very succ to ich (ich magnet) and it wound up infesting all my fish, lost all but 1 in a 125 tank, long story short, i had to start treating the water and water changing , all the methods you could try and meds available, really didnt completely get rid of it, What did work is Copper...yes copper , maintaining a 0.15 - 0.20 for 14 days killed off everything, and i also use a uv sterilizer , keep in mind, copper will kill all live rock corals and things like that, copper is ment for a fish only tank !!! and all is well now, im so happy....