They are very beneficial and serve an important purpose. They help keep your tank clean, besides I'm not sure you could get rid of them without killing everything else in your tank as well.
75 Gallon Reef 20 Gallon Sump/Fuge 6 X 54 watt T-5 lighting Octopus NW150 protein skimmer
i dont think much of anything will eat the giant ones i have in my tank, about 6-12 inches long, and about as big around as my pinkie, i have learned to live with them, i play a little game with them, when i see a big one, i spear it