Well I hear a popping noise in my tank at times and if I take the cleaner magnet and tilt it and let it go and make a low popping noise. 9 times out of ten I get a reply would a mantis do something like that. I'm all so missing a lot of blue leg hermits and a blennie a gobie and a mandarin. I did put some new live rock in a year ago. could it be??? I have never seen one in my tank but there is a lot of room and unfortunately I cant see the bottom of my tank to look for a cave or something.