Hi Bo,
Those triggers are smart little buggers, eh? A cowrie looks like a big long snail with a very shiny shell. At night they move around very quickly, and their heads seem to stick out more...but this is in complete darkness. Also, when it is night, they will clean their shells by releasing their body over the shell. During the day, ours always remain hidden in the rocks and toward nightfall, they will slowly begin to come out and start cleaning the glass.
Lynda