i saw a special on discovery in which they put a crab in a jar dropped it in with a octopus... he swam over grabbed the lid and unscrewed it...went in ate crab and left. i thought that was pretty cool, until they kept missing crabs in a tank on the other side of the room. thay set up a camera and low and behold at night the octo was climbing out of the tank and crawling over to the crab tank and eating the crabs and then going back to his tank.