I came home last night to find my long spined urchin sitting on the frag rack munching away at a piece of blue monti. He was almost completely through that piece when I caught it. I had noticed some of the same marks on a few other corals 2 weeks ago but couldn't figure out what had happened. It was an epic battle to get that guy out of the tank as he moves really fast and was able to wedge himself into every part of the tank. Also, he is about 10" across and I had to be really careful not to get stung. I had read that these guys will munch on coralline sometimes but had no idea they would just sit there and devour corals. Has this happened to anyone else?