Even since I have had my tank, I hear an occassional clicking coming from behind the rock work, possibly from a mantis shrimp. I have also seen a few crabs darting back and forth when everthing is quiet.
I have tried to trap them to atleast identify the species using the "plastic bottle cut and inverted" with a piece of fish in it with no luck. Every time I do that, my nassirius snails and hermit crabs get in there and eat the fish within a few minutes.
Any suggestions?