FWD is very useful in many saltwater aquarium creature including clams and most fishes. Since these guys can tolerate freshwater for a brief period of time while many small parasites can, it is a good way to eliminate the parasite from its host. You can literally see little crap drop out of the clam when you do the dip. Make sure the water is at same pH level as your SW though. But like Chris&Barb said, it is very stressful to any creature and should be the last resort.