I had 3 conches an absolutely gutted they have all been eaten the moon snail ate the 1st two so sumped it! This morning the last 1 was turned on its back and the foot had been torn off!! Occasionally after lights out I hear a clicking coming from the tank! Could this be a crab or a pistol shrimps doing? I did think mantis at first but haven't seen any eyes lookin at me an been searching for a while! I have found crab shells when tearing it down a while ago!