I had a problem w/ the regular Red FW's, and couldn't get rid of them. After several treatments at "recommended" dosages of Salifert FWExit, I got tired of the hassle. I put 6.5 bottles of the stuff in my tank, and walked away.
... Never did see any flatworms after that, but the rest of the tank kinda took a hit from the stuff. It's recovering still, but ... I still don't have those red FW's.
Fish and corals seemed unfazed, some snails didn't seem happy, and the bristle worms were
p-i-s-s-e-d, but... the big stuff all made it. Bugs and worms and such seemed to be the only other casualties.
Now if I could just get rid of the Acro-eating variety.
- Mac