Ich...
Cryptocaryon irritans...in a reef tank shouldn't be deadly. I can't say why, but I've maintained my reef for over six-years now and even on those occasions when it shows up it abates withing days and isn't at all serious. The only time I've seen it is following the introduction of a fish that wasn't quarantined. But, as I said, in my reef it simply passes. So, necsones...the first thing I'd do is check all your reef's water readings to be sure that there isn't something that isn't at proper levels that's stressing the fish in that reef.
On the other hand, I set up a FOWLR about two-ears ago and I'd had continuous problems with both Ich and with Velvet with the consequent loss of many beautiful and expensive specimens. Why these diseases are so virulent in a tank without coral is a mystery to me.
I'd tried everything from "reef-safe Ich remedies" to garlic without any success. The only thing that has brought success is quarantining with a
copper-based medication. Just recently, I had transferred all of the fish in my FOWLR to my quarantine tank where they were brought back to health with cpper-based meds. I left them in there for seven-weeks and left the FOWLR completely free of fish for that same period of time. Within two-days after I put them back into the FOWLR, the velvet re-appeared...causing me to return them all to the QT. Ich and Velvet were so stubborn in my FOWLR that I just very recently gave up the battle against them in that tank and put a copper-based medication...
which of course, you can't do in a reef.....into the FO...so now it's I can no longer keep any inverts like conches and starfish in there with the fish, and everything like pods and bristle worms have all died too. But, the fish are fine, which was my ultimate goal.
What I'm getting at is that I suspect that your water conditions may be off in some respect and you should do what you can to figure that out and correct it and that should address the Ich issue adequately in your reef. In the meanwhile, the best thing to do is to do your best to get all of the fish out of your reef and into a QT where they could be treated.
Take a look, here for some more info on Ich...
http://reefkeeping.com/issues/2003-08/sp/index.php