I had an emerald that claimed the same hole in a rock that my Royal Gramma did. After a week or so the Gramma lost. Crabs are a lot of fun to watch and I try to keep a variety but they can cause so problems. I remember on time I had an explosion of pods, it was crazy, had no predators. Noticed that my zoanthinds, which where very healthy where disappearing. One night stayed up and saw them covered in pods. Everyone said, can't be, zoanthinds must be sick, even thought they would open half eaten the next day.

Moral of story is everything in moderation, after putting in predator for pods the Zoanthids recovered and they stopped disappearing.

I say put them in, there is not a natural reef in the world without them.

Mike