Zoo predator?

[richtg]

Are there any commonly known reef inhabitants that may take to eating zoanthid polyps? I have several colonies, but one colony disappeared almost completely in stages-with no trace. One day they were there, and the next day, half was gone! They were firmly attatched to the rock and once gone, the rock was picked clean to the coraline.

I don't think that they simply detatched and floated away, nor do I think the colony died-as the rest of my colonies are thriving, and there were no signs of decomposition.

Any thoughts? Tanks, Rich.