Mantis or Pistol Shrimp?

[MikeP]

I've had a pistol/goby pair for about a year. He will "click" at night sometimes. A pistol shrimp wouldn't go after a fish as far as I know. They would go after a shrimp like a cleaner or peppermint. Investigate your tank with a flashlight after lights out and see what you find. Although my pistol will poke his head out during the day and stay hidden all night.

HTH