Melanurus Wrasse! I had the ugliest flat worm problem and he took care of each and every one! Ate flake, pellet and frozen food as well. He was always a model citizen too. I have a canopy, so a cover wasn't necessary, they do like a nice sandbed to sleep in, so keep that in mind. Flatworms can take over rapidly, whatever you choose to do to eradicate them, I would do it fairly quickly. Good luck!