I have long since sold my bangaii, so I,m waiting for some of my 5 Pyjama,s to pair up. Not sure if their young do the same as the bangaii young.
I do have a pair of Diadema,s in my tank though. Took care of a persistant alage problem on some of my older rock. Have not bothered anything yet, but I did post on a thread on RC, where they have been know to eat some corals like caps. We figured they cant tell the difference when eating coralline.
I experimented by placing a rock with part of a brown cap on it and lots of algae I wanted cleaned. Sure enough, they ate the algae and the cap.

I do however, have larger brown cap, that they clean around and dont bother. They seem to be very aware of large corals and their spines.
However, that only seems to be a trait in the Diadema, as shown in the destruction of my large bubble coral, from the pencil urchin a couple years ago.
