IMO only.....gona step on some toes here....sorry in advance.

I had one bad ICH ourbreak when I introduced my powder blue (imagine that, LOL) and it almost wiped out my entire stock.
I tried the hyposalinity and raising the temp thing and it didn't work for me. I also tried some checmical that the pet store sold me, no good. The next Ich outbreak that I got was after I had gotten into corals and some of my corals could not handle the hyposalinity or the rise in temp, so I then tried a REEF SAFE Ich chemical, same results as the other pet store chemical, no good. The only thing that I found that worked like a champ for me was a UV Sterilizer.

I know a lot of people are against them and a lot of people are for them but I kept one on my tank and will from now on and would only run it when needed. I never left it running for extended periods of time but it always did the trick.

I even tried to remove all creatures....let the tank sit for the entire life cycle of the ich, treated the creatures in another tank with Copper. I even waited an extra week and then put the creatures back in the display tank, got it again. I'm BIG on QTing my new fish for weeks too.

I didn't have it like all the time and would get small outbreaks here and there, kick on the UV, it would be gone and wouldn't see it again for months. I usually noticed it when I was slipping a little on maintenance and my purple tang was always the first to show it. Never saw it on my other fish. Kick in the UV, boom it was gone in a day or two and all was good. I always feed garlic and vit enriched meals to my creatures. It wasn't that bad. I read an article that said that all tanks have ich in them and getting COMPLETELY rid of it is impossible; it is just a matter of learning to control it and keeping it at bay.

Just my 3 cents!