I thought i had a mantis for a long time, hermit crab and snail deaths, LOUD snapping noise, but i finally saw him one night, a relativly tiny pistol shrimp! the snails and hermits fought all the time in my 30gl so they killed each other occasionaly. The only way to know for sure is to see it. I broke down the old tank and put the pistol in my 5.5gl with another pistol hoping they might mate.... havnt seen it since, my other pistol is prettier anyways, oh well. But no more snapping coming from the new tank.....