From what I have read when I wanted to set up my QT/hospital tank, you won't need to scrub it but you will want to take everything out of it including the sand and rock. If you ever have to dose in it, the sand and rock can trap or absorb chemicals and then bad things can happen. They also just recommend running simple sponge filters only. I am not sure what filtration you have on there, but you should be able to make it work. Most don't recommend running carbon either. The fact that it is already cycled is a good thing. Once you pull everything out, it should be good to go. My main concern would be the size. Will be fine if you only plan to QT small fish, but you might look at just getting a cheap 20+ with a heater and sponge filter. I found a good deal on a 40g breeder at PetSmart. I wanted to be able to put anything in there for a month or so. Good luck!