Did you move your fish to a quarantine tank? Do not try hypo in the main tank, you will kill all the live rock and sand and any snails or inverts in the tank.
I had ich years ago in my 90g reef, and no tank large enough for all my fish (hippo tang included)...the ich meds for a reef do not work but make the inverts and coral sick looking. I decided to give up on those "cures" but try giving my fish fresh garlic juice soaked shrimp chunks, it helps to build their immunity up. I did very careful water changes trying not to stress the fish. I did not add any new fish for fear that the new would be stressed and get infected and then it would spread like fire.
After a year of no outbreaks, I never had another problem with it. I did learn that a simple QT for new fish would have saved me all kinds of heartaches. I have since moved the tank to my new home 3 years ago (moving is very stressful), to date not one ich spot.