Tuxedo's are really great urchins the can mow the heck out of some algae, but they do tend to mow more on coraline and quickly. When it comes to coral they are pretty gentle. I was watching mine the other day, it was sitting on a Ricordia. At first, I was a little worried that it developed a new taste for things, but I looked a little closer and it was munching just the very edge the coral on some rock.