A few things I've read:
1) Tropic Marin Pro Coral Cure
2) Levimasole Hydrochloride - a treatment some people use on AEFW with success in their reef tanks (and can be found at feed stores, apparently)
3) The
Chelidonura varians nudibranches, which apparently exclusively eat flatworms. Not sure how available they are here/there, though?
One thing to mention is that, in my short reading on the subject, everyone seems to be saying the same thing: none of the treatments get rid of the eggs. Those need to be manually removed/scraped off.
This sucks...sorry
But good luck.