Is there a crab in my live rock?

Question
Hello Jennifer,I saw a similar question on the website.  Someone mentioned that I may have a crab in my live rock that killed my blue streak goby.  He just dissapeared completely.  I later added a pepperment shrimp that hid in the rock that I found 3/4 eaten about two days after being added.  The last victim was my blue starfish.  He crawled into my live rock about two days ago and today I came home to find him torn apart limb from limb.  All of these happend a couple weeks apart from each other.  I'm just wondering if a crab could be causing this, or what is?  If it is a crab, what can be done to get rid of him so that this doesn't happen again?

Thanks,
Nathan

Answer
Hi Nathan. It sounds to me like you may have a hitchhiker and an undesirable one at that. You may be looking at a mantis shrimp hiding in your live rock. They are the only creatures with the intelligence to not get caught, appetite and strength to do as much damage as what has happened in your tank. It may be something else hiding in your live rock but whatever it may be it is a predator and you'll need to get rid of it. Catching a creature that is hiding in your live rock is virtually impossible. If you've never seen it then chances are you will never catch it. The best way to get rid of it is to remove the rock it is hiding in, making sure to block any backdoor exits to prevent whatever it is from escaping and hiding in another rock in your tank. Once removed you can do whatever you want with the rock. I've heard of soaking it in fresh water to flush the creature out, pouring carbonated water over the rock, letting it completely dry up for a few weeks to kill the predator even boiling the rock(that seems a bit drastic to me). The only other solution would be to set a trap for the creature somehow. If you are dealing with a mantis shrimp, keep in mind that they are very smart and can outwit most traps set for them quite easily. Another way to capture a mantis shrimp that would work for anything hiding in your rock involves the use of a suction to trap the critter. The exact location of the creature's home cavity must first be determined, and the hose of a strong filter is then secured tightly over the hole. The system is left to run overnight, and the pest is invariably found trapped inside the filter when morning comes. In order to work, the creature must be of a manageable size, the location of its hole must be precisely determined, and there must not be any other escape routes within the rock. Good luck! If it is a mantis shrimp watch your fingers! They don't call them thumbsplitters for no reason!