I've had excellent luck with Flatworm Exit, but I've found you have to overdose by 40-50% of what the directions say (I follow all other parts of the directions to do a T).
As I said, if there's a fish that you like, that might eat flatworms, there's no harm in trying that. I've just seen too many people (myself included) who have gotten a fish they didn't really want because they were told it eats flatworms, only to end up with a tank full a flatworms a fish they don't like and can't catch.
I was right in your neighborhood over the weekend. We tried Cafe Muse for the first time (we'd been thinking about it for a long time, but never got around to it.