Here is an idea that most people probably have not tried, but which was VERY succesful in my reef tank.
You can't treat ich in a reef tank. There are no effective medications that you can put in a reef.
This is generally the case, but here is an exception. It's called MelaFix. It is available at Wal-Mart (of all places... who would've known). It is one of those cheap medications for a lot of diseases in fresh and saltwater aquariums. It claims that it is safe for reff aquariums and corals and inverts. I have mushrooms, shrimps, LR LS 6 linds of MAcro algae feather dusters, anemonies, sponges, and also angelfish, clown fish, damsels and scooter blennies. I had a problem with ich and treated with this stuff (in smaller doses than they suggest) and the problem was irradicated and nothing died!
Anyone else tried this?
The only problem with it is that id causes a small bit of bubbling when treating, and can cause your protein skimmer to bubble over... they reccoment turning of skimmers while treating.
As far as I can tell this method is by far the cheapest, and it was VERY effective for me!