@Pat, exactly my thinking and belief. The qt's, the ones I call prison tanks can't be good for stressed fish. So I have sand and a few small pcs of rock in mine, along with fake plants. I can treat prazipro and CP in the tank, can easily remove the rock for the CP if needed. If I have to use copper, I just know it will take a lot more to get it to theraputive levels. And I'll take out the rocks. I think of it more as an observation tank and a tank to allow the incoming fish to adjust and fatten up. I have an aquaclear hob filter, the largest they make so it is like triple the filtration.
I'll be turning my 39 gal display refugium into a QT tank. The majority of the sand and live rock will go into the new tank and sump but I'll leave a couple pieces in, and a much thinner layer of sand. Again, if I need to, I can remove the rock to the sump temporarily. That tank will allow me to qt tangs. It sits close to my display tank in my office, not 10 feet away but I can't do much about that. It has a canister filter but I'll buy another aquaclear and have 2 and take the canister off--it's too hard to deal with if I have to add carbon or take it out. I plan to use that has a vacuum for my sump--suck out crap, return water back