I just went through this, I moved all my live rock and hermit crabs to a QT tank for 1 month. Treated the main tank with Quick ick (malechite green) 3 day treatment got it from Petco. My fish are doing great all the ick is gone, put all media back into filter to remove medecine from water. I put the hermits back in. Just waiting for at least a full month to put the LR back in just in case any ick is still alive in that water.
This was the first time I tried it this way, usually i move the fish to the QT tank. I think this worked better, less stress on fish. For now I decorated the tank with some fake stuff so the fish would feel at home.
I used copper treatments before but they take longer to work and i lost fish to the copper before. copper is very tough to work with.