Have I got an urchin for you.
The hairy pincushion red/white striped relishes it, apparently. I just got one and, though the size of a doorknob, he's maneuvering with fair delicacy through my sps and lps in my 52, and has festooned himself with caulerpa as a future snack: he's spent all day trying to pull down two large stems and has not knocked down the local rockwork, which is not as well-seated as I'd like.
Got him from liveaquaria.com. Tripneustes gratilla is his scientific name. He's noshed just slightly on bubble algae, will eat the red stuff, and seems to like caulerpa best.