I've never used FWE to treat and have read that it's not as effective as other methods of treating/dipping. Red flatworms are the type that won't munch on corals, just irritate them and not just acros. A lot of wrasses will eat the red ones. AEFW are usually harder to see because they will match the color of the coral they are on, I think that's why, at least in my case, wrasses don't eat them unless blown off the coral.
Bayer will kill AEFW but it's not an in-tank method of treating them. I posted in the other AEFW thread a post from ReefCentral where a member used a cattle dewormer as an intank method of treating AEFW. He did have some complications in the tank after treating that could have been a caused by using this treatment, I believe from the flatworm die off since they can release toxins.