If ich was only in the slime coat.. wait.. they actually burrow under the skin..
You can remove all the fish from the tank, treat them to hyposalinity while the tank sits fishless for 6 weeks, remove all the fish and treat with copper while the tank sits fishless for 6 weeks, remove the fish and use the 3 day transfer method with 2 tanks then let them sit in qt for the rest of the six weeks.. see a pattern? Hehe!
Seriously, though, now that your tank has ich, you can try to treat it, or cure it. There are no reef safe, yet effective 'cures' that can be done in the display tank.
Hyposalinity, Copper, 3 day transfer- all will cure the fish of ich, but you're left with ich in the main tank if you put the fish back before the ich can starve without a host.
You can try to treat with garlic, good water quailty, food additives, and luck- works for some, and they don't see ich but maybe once a year, or when the fish becomes stressed.
