LOL You guys are awesome, thanks for the help. We will only pull the rock out as a last resort because there is an anemone with his foot planted in a hole in the same rock. I was <---this---> close to catching him last night. I just stuck a drinking glass in the tank with a raw scallop in it. He went right for it, but the rim of the glass was too slippery for him to get into it. Im going to rig a new trap and try again tonight.
BUT we did catch either a Cirolanid or Aegid isopod. And I thought the crab's beatie eyes were creepy... lol