I had an unidentified damsel that ate them, unfortunately I lost him to a marine velvet out break

The other thing you can do is to vacuum them into a micro filter bag. This works really well if you have a sump or when you do a water change. Just get a smaller diameter hose and suck away.
After a while it seems to collapse the colony and they all vanish:grab:

a friend suggested a leopard wrasse to me..i'm also looking.

leopard wrasses are pretty common actually.. there have been a bunch at the stores over the last few months... No idea on their flatworm eating capabilities though.

I picked up a nasty flatworm problem in my qt tank - following the proper dosing as dictated on the FWE packaging; had no effect... Finally got it sorted - here's the catch, you totally ignore the salifert instructions...

Do your w/c first - get out all the flatworms you can get (turkey baster and a bbs net works pretty good). Then do a 4x dose of FWE, then let it stew for 24 hours... (This is the reason for getting ALL the FW's you can out). Then turn on carbon. Repeat 5-6 days later.

Use at your own risk, this worked for me - but I take no responsibility for any deaths / meltdowns from this this method. We seem to have a nasty resistant strain of flatworms that have been going around calgary.

update: I got a Red Coris wrasse about 2 weeks ago and he won't touch the flatworms!!! :(

The flatworm colony is now massive, litterally every rock is infested..

My wrasse seems to do a good job- rarely see any flatworms in my tank now.

wanna rent him to me sometime? :P

What type of flatworm problem do you have? Beyond smothering your corals, I've read that the common red planeria is no real threat.
I had a small break out of flat worms but it took care of itself with more diligent tank housekeeping. It seems that the 'fix' to these types of common problems are the same thing - reduce phosphates and excess nutrients. Supposedly every aquarium has flatworms, but they are only noticeable during a break out.

Have you tried increasing your skimming, water changes, flow, and less food at feeding time?

just increased my flow today and we are going to start syphoning everyday

frequent oceans and perhaps you may find one there. They are pretty cool fish and reasonably priced