There is a treatment for Ich being researched involving moving fish between two QT tanks, sterilizing each tank between moves. There's a sound theory behind it, but no hard data yet. I don't really see it as being any easier on the fish than hypo or copper.
Otherwise, you only need enough QT to house all the fish. Leave the inverts in your display without any fish at all in it... they don't carry Ich, but your tank needs fallow time for the ich to be removed from it. Treat your fish with copper or hypo.