I got a few pieces of live rock a month ago and a small mantis shrimp hitch hiked into my tank. I knew something was up when I started hearing clicking noises coming from my tank at night and started finding dead hermit crabs. I only managed to get a good look at it once. It's very dark colored (black or green) and is about 1 inch long. How could I possibly trap it, and discourage it from preying on my crabs in the meantime?