Well, IMO I don't use medications for Ich. Period. The last time I used medication in a QT was on a freshwater Piranha with Dropsy back in 2002 ish. Dropsy is a disease that is expected to be fatal, so the medication was really a last ditch effort. Surprisingly it worked, even after a secondary Ich infection. Tough fish!
Oh ya, back to the topic...I'm going to start up a QT for my tank too when I get the jawfishes and wrasses. I will medicate these fish with Prazi-Pro since the Jawfish are often wormy...I would do the same with any Tangs, and a few other species. The Wrasses will just get hypo for a few weeks.