I have a blue tuxedo urchin also, he's cool. I don't feed him anything and he's been in my 24g nano for about a year.
I also have a purple urchin in my 55g. The only thing you need to "worry" about is if your corals are loose on your rocks they will get knocked down by the urchins when they pass by them. Also, if you look at
this thread I started you'll see what else they do. It's pretty entertaining but sometimes it's like ok enough's enough!!
In fact just last night my purple urchin got something.... I'll post in a few.
Oh just make sure you don't get a Rock Boring Urchin. I don't usually see them for sale but I have two hitchhikers in my nano that started out the size of my pinky nail and are now bigger than golf balls and next to impossible to catch because you cannot remove them from the rocks, they "anchor" themselves.... They are starting to outgrow my tank so I'm trying to get them out. Got one the other day, one to go.
Other than that, I think they are beautiful and pretty darn easy to keep.