Sea Egg (urchin, Tripneustes spp) not good for reef tank?

[Chowder]

I have one in my tank. The problem with them is they get large and like to move through your corals and dislodge them from there purches. Mine occasionally has zoas , Sps frags and other polyps and rocks attached to it. This weekend it was moving around the tank holding onto a 4" piece of egg crate and knocking over everything in sight. It won't really harm anything but will move the unmounted and some mounted pieces around your tank. The odd piece will get lost in the rock work.

Chris