I just setup my tank a few months ago. Every once and awhile I would hear popping sounds. Sometimes its once and awhile and other times it pops like crazy. I just noticed my snails and hermits dying one by one and they are all in one corner of the tank. The pops are pretty loud.... I dont know where the sound is coming from(fuge or main). How can I try to figure out if its a mantis or a pistol? Also how can i trap it?