No urchins as the post states, and I don't have any crabs (not even hermits).
Come to think of it, I have many of those! Could they be the culprit? How to get rid of them, and should I?
It is when you do see rocks
I am not as lucky as you where my rocks are hidden by my corals (at least not yet)
So then based on this, it could be the single chiton I have, or the asterina starfish. It might be the starfish as I have started to notice their population going up recently.
I don't want to remove something beneficial that doesn't need to be removed. And now after what reefwars said, I am even leaning towards leaving whatever is eating the coralline alone.
I am not too worried about it, but I like the coralline look and just thought to mention it to get some thoughts from the experts.