How to make a quarantine tank/hospital tank

[mikeclarke]

What I've read and been told is to have no carbon in the filter as it will absorb anything you treat with. I've also been told the same with a sand bed and live rock. If you don't have any sand or live rock, how do you have a biological filter to handle ammonia and nitrites?

I have a 20 gallon that I've tried to use as a hospital/quarantine but haven't had any luck.

Any suggestions? Do I need a uv filter and skimmer like my big tank?