I had one in my tank that used to drive me crazy
... Every night when the lights went off he would snap away ... I thought it might be a Mantis but there were no livestock losses to spek of so it had to be a Pistol Shrimp ... I think I squished him when I was moving some rocks around about a year ago cause I found a claw in the sand and no more of that darn snapping ever since
Cheers