Rock urchins with corals

Hi everyone,
I just ordered some urchins to help keep the sides of some of my coral tubs clean. I ordered black urchins and rock urchins from this website: http://www.mysaltwaterfishstore.com/Urchins/
The black urchin I believe is Echinometra lacunter the rock urchin I don't have an ID on. I have a couple questions for people. First off if anyone knows a species name of the rock urchin that would be awesome. second I have kept Echinometra Lacunter with coral before without any problems but reading last night in Reef invertebrates by Calfo and Fenner They were suggesting that many of the short-spined urchins have a reputation for puncturing coral skin. I would imagine this would be an issue in fleshy corals like euphyliids and various anemones. Has anyone here had this experience or any other negative experiences with them, such as consuming coral. I know they are bulldozers but I can live with that.
Thanks,
Kyle

I love a good read,and calfo certainly delivers. On the urchin is it possibly a Echinometra sp? If I recall that is what my brother had in his tank for a long time and I don't recall anything bad happening.We read that some of them can be rock boring but not the one he had.

yea Calfo is usually pretty good. It very well may be an echinometra species Im just not certain. They come from Florida if that is any help. Guess ill find out all about them when they get here on tuesday