I have a horrible flatworm investestion as well, they cover the sand and some of the rocks, they generally don't go on my corals but when I first noticed them I bought a sixline wrasse and he doesn't seem to like the taste of them. Then I bought a Blue Velvet Nudibranch which was eating them until my powerhead ate him. Last month I just added a mandarin and he doesn't really seem to like them so I am just waiting for their population to crash as well. One thing that I have been thinking about, where either of you running ozone when their populations seemed to diminish?