I would not use any thing smaller than a 10 gal. the bigger the tank the easier it is.
for the meds, it all just depends on what is wrong with the fish. I dont keep any thing. cause my luck I would go out and spend money on all these meds and then not have what i need. a lot of people here do the hypo on there qt tanks. but if i was to keep any thing in there i would keep Maracyn II (saltwater type) it does internal and external parasites. but i do have to say that i have copper under my tank but i have never used it. but make sure you dont put them in with your inverts.
mike