dead snail shells with holes

[Scavenger]

My first thoughts are mantis. Given the short term demise of lots of snails and the fact the "evidence" is piled in a small area.

Listening for clicking at night and setting up a bottle trap or similar would be my top priority at this point. If it is a mantis, darn near everything in the tank is at risk.

All this is just my opinion, it has no scientific, horrific or other ific evidence or knowledge. <grin>