[Ernie]

I had a mantis shrimp hitch in on a piece of live rock, too, and he wiped out all of my hermits and a couple of cleaner shrimp. He was also constantly hammering on a piece of live rock, making an annoying clicking noise. I read somewhere this burrowing through rock and hard surfaces is dangerous because they can crack through the glass of an aquarium (though I've read not all species do).

It took me a while to trap him. They are fast, smart, and reclusive (and UGLY, imho)!!! You might let the local fish stores know that you're interested, and when the odd customer calls to find out how to get rid of an unwanted one, you may be able to score it on the cheap.