We just got some new zoas. shortly after we got them in the tank, like the next day, our sailfin tang took to nipping at both colonies. The one colony didn,t seemed to damaged, and are open. The other, a green zoa with about 7 polyps has not opened since. All but three have small chunks missing from them. Should they recover? they have been closed up for about three days now... I thought tangs were supposed to only pick at the algae not polyps....