As Mike & Matt suggested no medication should be used in a QT tank unless there in an indication that it is necessary. A QT tank should be thought of more as an observation tank.
The use of a UV sterilizer is also not suggested as it will kill bad as well as good bacteria. I also never suggest the use of a canister filter on any tank since the bacteria in them dies
very quickly if power is shut off and can cause you a lot more issues if released into your tank.
Unless you plan on purchasing larger fish a new 10g tank and an inexpensive Accuclear filter, an additional package of 3 foam filters, a 50W heater and an airpump and airline with airstone should be all you need. And a few pieces of PVC to make it feel homey

I suggest the Accuclear for a 30g tank. It will take the solid crud out of the tank and keep the surface of the water moving well for oxygenation purposes.
Take one of the foam filters and drop it in your sump and leave it there allowing it to colonize with bacteria, when you need to QT a fish take it out & pop it into the filter and replace it with a new one (which will colonize within a couple of days).
If you need to medicate the QT tank, don't use the carbon.
The airpump/line/stone IS for when you need to medicate as most medication stresses fish further and additional air helps reduce the stress, especially when you are dealing with an illness that affects the gills.
Painting the rear & sides of the QT tank will also add to the comfort level of the fish, though you can also tape on the dark background they sell at LFS's.
If you need a hood & standard light for it- drop me a PM, I have one I can give you.
The $40 or so dollars that it will cost to put this together will give you a lot of peace of mind when buying new fish !
Oh..and you want your parameters as close to your DT as possible so you don't go and stress the fish when adding him to your system
