Those are amphipods. Great fish food, my damsel loves them and sometimes doesn’t even eat the fish food I feed him because he’s full. I see him pick the pods off the rocks, he’s always looking around for them. I had some hitchhike in some Chaeto I put in my fuge and they populated my main tank from the return. They keep the rocks and substrate clean. Free CUC & fish food! Haven’t had any problems with them bothering my Zoas or any other corals.