To set up a QT/hospital tank here's what i do i run two HOB's on my DT The smaller one is used for the QT it's kept filled with poly-fill so it can hold a good sized Bacti-base fill the QT with water from the main tank put the small hob on, put some pieces of PVC in so the fish have place to hide as this will help lower stress,
run the QT bare bottomed easy to clean later. you will get a small AMO spike after 2-3 days so be ready to change a little water.
After your done with the QT clean everything with vinegar and fresh water Toss the old ploy-fill repack the HOB and put it back on the main tank to ready it for the next time.
this method has worked for the past 11 years for me with no problems. oh get the poly-fill from a craft store much less costly A big bag cost 5-6 bucks and last yrs. One more thing (sry) If you keep the QT full it wont be long before it becomes a Display tank lol