What is this urchin?

[BrettDS]

I got quite a few of these guys with my live rock. There are at least 6 or 8 that I can see in my 75G tank and probably more in the rocks.

They are reasonably small, but seem to be growing... The spines on that guy are probably 1/2 to 3/4 of an inch long and he's one of the biggest.

Are they harmless or something to worry about?

 

[cloak]

Rock Boring Urchin perhaps? (Echinometra sp.)

http://www.reefkeeping.com/issues/2003-11/rs/index.php

 

[BrettDS]

Thanks for the reply. Very interesting article.

This new tank is definitely all about the urchins. Like I said, we got a bunch of those little black/deep purple ones with my live rock and this one large light purple one with my live sand. The kids have named him fuzzy.

 

[Shawn O]

Bonus! Lucky to get a good hitchhiker like this.