When I had ich on a Hippo Tang I found that raising the tank temperature (was 79 to 80 degrees, now 81 to 82 degrees) resolved the problem with no recurrence.

i set up my new 20 gal reef....and my tiny blue tang had a ich outbreak...covered in it....i did nothin but feed it flake soaked in garlic everyday...twice a day....cleared it up in a week...havent had ich since....this was 2 months ago