most quarantine tanks will have bare bottoms (for easier cleanup afterwards), a fake cave or pvc pipe for shelter for the fish, a small filter (either a HOB or sponge), and a heater.
I like to use a filter that takes the same media as other filters I have. That way, I can put a "cycled" filter pad in the tank easily, and also have to buy fewer kinds of media.
20 long tank, Fluval 3 internal filter + 1000 lph powerhead. Lots of plastic pipe. 27 Watt PC light plus a 100 watt heater. I QT marine fish in this for 6 weeks, works real well, change 5 gallons of water or so a week