What kind of urchin is this?

[Gatorfreak]

I've counted 8 of these so far that came on my LR from liverocks.com. They are all very small but growing pretty fast.

 

[dustybrannum]

i have two and there spines are about 3 inches and still growing fast.

 

[steve-s]

Looks like a purple rock boring urchin (Echinometra mathaei). Very very efficient coralline strippers.

Check <<this article>> and see if you find the right one.

Cheers
Steve

 

[Gatorfreak]

I haven't noticed any coralline stripping yet but they are very small still. It's hard to match them with pics of full-grown urchins. I'll probably remove all but 1 or 2. Eight just seems like trouble, especially when they start getting big.

 

[Fluff]

I had 11 at one time. I gave a few to friends and the rest, all but one, to the fish store. They do eat your coralline but I've also seen mine eat the film algae off the glass. The only issue I have with mine is that it will knock/push my corals around. They are neat but not very graceful.

 

[quarryshark]

Don't have that kind, but I have 4 urchins in my system. I have to watch that they don't knock down my power heads, but other than that they are good citizens.