FWIW,
IMO, every tank has flatworms in it. a lot of people say that they come and go. i would not use the flatworm exit yet, instead try increasing your flow to the areas that you see the majority of them in. flatworms have a very weak gripping ability, meaning that they can not hang on to the rock or substrate very good. they say that with enough flow you can get them to naturally disipate. you could also try getting a six line wrasse to eat them. i guess you can tell that i dont like to add chemicals unless everything else has been treid.
HTH and keep us posted.
