So I have a 30 gal tank with 3 triggerfish and liverock in it. There are no other fish. Occasionally, I hear sharp popping/clicking noises coming from the live rock, and the sound is usually followed by a small bubble coming from the live rock. However, when the sound occurs, I usually also see one of my triggerfish nipping at the live rock. Could it be possible that the sharp noise is coming from their teeth grinding against the rock, or would it be a possible hitchhiker? The size of my triggers range from 2-4 inches should I be worried about any of them getting attacked by a mantis or pistol shrimp? Thanks.