this is off nano-reef.com
"A CBS is a mean shrimp. They are omnivores and are very territorial. Your tank is over crowded at 6 fish for its size and the CBS most likely is reacting the way it is because it feels threatened by the fish encroaching on its territory. It also may sense that the tang is either diseased or weak and is thus trying to make a meal out of it."
help! problems with coral banded shrimp and blue hippo tang - Nano-Reef.com Forums
Ive read it a couple of times, never experianced it my self but i wouldnt take the chance of having a shrimp eat a fish, when its suppose to be the other way around