Possible predator in tank
I had a conch in my tank that has been there since I set the tank up about one and a half years ago. Yesterday, its shell was empty, and there was a hole pierced through the back of the shell. I saw it moving around normally two days ago.
I'm trying to figure out how this could have happened. The tank has a yellow-tailed blue damsel, a clark's clown (about 5 cm) and a royal gramma. Apart from that, there are some hermits, a urchin and a couple of small hitchhiker crabs.
I do hear clicking sounds from the tank occasionally, they've been there since I set the tank up. I've read that this could mean that I have a mantis or a pistol shrimp somewhere, but I've never seen anything like that. How big would one of these have to be to be able to pierce a 6-7 mm hole in a conch?