FW dips stress fish. But, they can also make the parasites that are attaching to the fish drop off. parasites that have already burrowed into the fish stay comfy and warm where they are though. basically, I wouldn't do a FW dip unless I was sure the fish could take it. I also wouldn't use a FW dip as my only form of treatment - temporary relief at best. Your best bet is hyposalinity 1.09 for 6 weeks.