I tend to think of urchins as the "hey neato!" critter in the tank. Mine eats mostly coralline algae and poops it out in nice piles. I wouldn't risk it as they can also go through a huge amount of coralline (and any other algae near the coralline) in a short time.
On the other hand you could try one for a few days and see what happens. Make sure there is no rock shifting though or he might go squish.
__________________
Christy's Reef Blog
My 180 Build
Every electronic component is shipped with smoke stored deep inside.... only a real genius can find a way to set it free.
|