These are the worst thing to have in ur tank. I know I had them in my last tank.
What-ate-the-clam?
http://www.socalireefs.com/forums/showthread.php?t=26814
They only feed on crustations, clams, snails, crabs
I fought them for 6 months with no crustations in the tank and still had them after 4 months with no food for them. I ended up taking the tank down and drying out every thing. I killed all the corals and live rock. I did not want to transfer these things around. They r a nightmare. Please don't trade with any one for a while u need to put ur tank in qt.
How to bait and catch them.
Things u need live rock piece, fishing line lone enough to go to bottom of tank and stay out of water, and a piece of shrimp from market.
After ur lights go out tie a piece of shrimp to the live rock and drop it to the bottom. About half way through the night check the shrimp with a flashlight. Be fast to. These thing move quick.