A ten gallon with a glass cover, a seasoned sponge filter, a heater and some non-calcerious decorations would do. You don't want sand or live rock in the tank if you can help it. Many meds will get absorbed into them, and the sand can acctually help ick and other parasites to breed, by giving them a substrate to complete their life cycles.
I wouldn't advise trying to squeeze more than one fish in the QT at a time, because of aggression and other factors. You want to make sure the fish in there will eat what you offer, and is healthy for at least 30 days before you add them to the display. I only have a ten gallon right now, with room for one fish. When I set my 120 back up, I will be sure to QT eveyone I put in there. It's a great way to protect your investment (either monetarily, or the lives of the fish) of what you put in the 110. Jen
