hitchhiker ID - video

Can anyone ID this critter? I know its not the best because as soon as it sees me move the camera closer it takes off in to the rock, but watch this video a few times, between 4 and 5 seconds you'll see it on the rock and then it disappears back in to the rock.







It looks like some sort of crab? Zoa spider? What do you think? I'm wondering if this is why it is impossible for me to keep zoas in my tank if this critter isn't munching on them. This critter is the main reason I'm thinking I might not reuse my rock in my new tank (or I may move it in to the sump to keep this little guy from getting to my corals) at a minimum I will probably soak the rocks in cold RO/DI water to try and coerce all of the creatures in the rocks to come out of the rocks before I move them in to my new tank...especially that little thing! But I have lots of bristleworms too that I plan on freezing out again because they come really sluggish in cold water and come out of the rock and let you pick them out with tweezers. Hopefully whatever this thing is does the same...



I hate to lose all of my coralline algae, but it is the price I'm going to pay I think...