Do you have a hospital tank??? You can not treat fish with ich in a tank that has LR, SS or inverts. Your 2 choices is hyposalinity or copper, with hypo being the preferrable.
Otherwise, if removing the fish is impossible, then going with one of the so-called reef safe meds is all you can do. I've never used them, and don't recommend them. They have limited value in address ich and I have seen ill effects on inverts.