I just bought a pistol shrimp which i knows makes a poping noise in my tank, but before this I have heard a similar noise. I was wondering i might have a mantis in my tank. I have had some fish just disapear in my tank, but they were leopard wrasse which are hard to keep. I can never find any remains, the guy at lfs says the crabs eat them... I was wondering if anyone have any ideas how to find one of these buggers or how to get them out...