Here is a picture of a species of Flatworm that I have been fighting. So far I have found them on Euphyllia, mushrooms, Ricordia, Xenia, Cabbage Leather, Colt Coral, and Lobophyllia. Fortunately, they do not bother rough feeling corals such as most SPS. They prefer corals with a slimy touch. Flatworm Exit only seems to be semi-affective against them. I was able to eradicate them in one tank using about 3 times the recommended dose. They fall off the coral instantly when the coral is swished around in freshwater. So far, this seems to be the best treatment. They blend in very well with tanner colored corals such as leathers. If you had never seen a flatworm before, you would swear it was just part of the coral. Fortunately, I have almost eradicated them through a series of freshwater dips. Unfortunately Xenia don't seem to like this much though.