I recently had a velvet outbreak in my 220 FOWLR tank and have transfer all the fish to a hospital tank for treatment. I want ahead and treated the display tank with cooper as well and levels have maintained but it still makes me feel uneasy that he won't get fully treated. I know velvet is a fallow period of 6 weeks and ich 76 days but I really don't want to wait that long. My question is if I were to drain the vast majority of water out the tank just having some water left on the sand bed and filled it with rodi water would that be enough to kill any parasites? Or will someone survive in the sand bed or rocks?