When I 1st saw it, it was hitting a rock upside down, with it's head!. I could only see the tip of it and was so shocked that it was there that I didn't get a good look. It scurried away pretty fast. We have been hearing popping from the tank & thought for months it was a problem with the filter or...? It sounds like snapping your tongue against the roof of your mouth. It pops about every 3-6 seconds sometimes. I have no picture (can't even really see this guy). He is hiding in a hole in the live rock also.