This was talked about at Trouble Free Pool here. Basically, the moss is not a sanitizer in the bulk water so you still need chlorine (or other EPA-approved sanitizer) for that purpose. Notice that the example has someone with an SWG system yet they complained about having chlorine splashed on their clothes as if adding it manually. They also talk about a significant reduction in chlorine usage so presumably lower SWG on-time, but they could just as easily supplement their pool with 50 ppm Borates for algae prevention (or $2-3 worth of PolyQuat 60 weekly) for the same efffect allowing for a lower FC level.

Richard