First, I want to compliment you that your tank looks very cool -- natural, lots of coralline and beautiful fish....but....
I am pretty sure the fish "alarms" are going off. My observation in watching fish in my tank is they sometimes they just get "spooked" even for no good reason. They knock over all kinds of things -- rocks, frags, snails, or bumping into something. I couldn't figure out why my clam was falling off his rock. So I setup a time-lapsed videocam -- turned out my lawnmower blenny would get spooked and was knocking him off. Its doesn't happen much, but it took me awhile to figure it out.
IMO, I think its just a matter of time a fish gets spooked and gets one of their fins caught. If you have a dinner-party and wants to temporarily impress friends maybe its cool-effect, but in the long-term it will probably bite you. You're better off attaching magnets to the glass/rocks and making rock ledges instead.