ID urchin please

[Victoria]

I found this in my tank about three months ago. I have never put an urchin in this tank. I did transfer some live rock from a tank that had one. When I found it , it was the size of a pencil eracer. It stays for the most part in the back of the tank, behine the rock work. Will It cause me trouble later? Its pretty cool.
Victoriahttp://reefcentral.com/gallery/data/510/27404sea_urchin_005.JPG

[Travis L. Stevens]

Rock Boring Urchin (Echinometra mathaei). It's fine. They are strong and can knock loose frags over. But all in all, they won't do any severe damage.

[Victoria]

heres a close uphttp://reefcentral.com/gallery/data/500/27404sea_urchin_002.JPG Wondering how it got in my tank?
Victoria

[Travis L. Stevens]

<a href=showthread.php?s=&postid=7125641#post7125641 target=_blank>Originally posted</a> by Victoria
Wondering how it got in my tank?
Victoria

It hitchhiked. Just like their name implies, they burrow deep into the rock. It was hiding/hunting, you plopped the rock in the tank, and viola! You have a hitch hiker

[Victoria]

Do you know how large they get?