Have flatworms? These guys eat them as fast as they can find them. The blue velvet nudibranch (pronounced new-dee-brahnk) AKA Chelidonura varians is a specialized sea slug that eats flatworms exclusively. Its head is shaped like a hammer, and it has a split foot that mimics the shape and movement of flatworms. These bizarre creatures also have a built in defense mechanism to inhibit predation; They incorporate the toxin that red planaria (flatworms) produce. This makes the nudibranches themselves toxic. Although they may have a good defense from predation, these animals are defenseless against overflow boxes and powerbeads. So if you plan on using one to eradicate flatworms, you should plan to block such obstacles with screening or sponges. By a twist of fate we have a Springeri psuedochromis in the the store right now as well, and I swear these guys mimic the coloration of the nudibranches. Pictures in the gallery.