[canadawest]

All of the above suggestions, including the garlic, but most importantly....

Leave everything alone!

Ich is an opportunistic parasite that most commonly affects fish with low immune systems due to stress. The abrupt change in salinity could have been a contributor, but not likely the only cause. Is this a new addition to your tank? Is it a Tang?

Just try to keep things stable and stress free for the next week, and likely the Ich will just go away as the fish regains it's immune system and calmness. Try to keep your hands out of the tank (stresses the fish), and keep water parameters (Temp, salinity, pH, Nitrates, Nitrites, Ammonia) as stable as possible.

If the Ich doesn't get better after a week, or gets worse over the next couple days, I recommend Kent RxP, a treatment product that is reef-safe, and something I used last year to help my Blue Tang deal with his Ich. He had it at least three times in the first 6 months I had him, and not once in the past 9+ months. No other fish ever got it while he had it, so I know it was just him getting used to the new environment. Contributors were "first two weeks after introduction" stress, high temperature swings last summer, and new tank additions.

Now he's rock solid, and Ich hasn't reared it's ugly head in my tank for almost a year. (Knock on wood). ;)