Please identify this urchin
 

I bought this feather duster long time ago, and this urchin was stock in the small piece of rock that the FD tube was hosting on, so I pulled it off since it was too tiny and I didn't want any unknown hitchhiker in my tank, but after I pulled it out I thought it looked like an urchin so I put it in my tank thought it would be a neat addition to the tank with such a tiny urchin.

Within a matter of....about three month, the urchin gas grew dramatically....I've never seen one grow that fast...I have three other urchin large, medium, and small one for each size and never changed in size for a whole year at least.

Two pictures attached, the urchin now, and the ACTUAL size of the urchin on my palm when it was found 3 months ago and now...

A quick ID would be helpful and perhaps some info on it, it only comes out at night and dodge really fast when I use a flash light on it...moves very fast unlike urchins =.=" Just wondering if I should start worrying...Thanks!

rock boring urchin

HAHAHAHAHHA. I love the picture of you holding it. Awesome.

Echinometra mathaei

+1

Aka "math" urchin - Echinometra mathaei.

Fairly hardy but have a rather annoying tendency to rearrange rockwork in our tanks. Mine is sumped at the moment because I grew weary of fixing the landslides. I bought mine because, well, I do kinda like them, you see them all over the place in Hawaii and I like Hawaii better than Calgary but I live in Calgary and not Hawaii so anything I can do to remind myself of Hawaii is a good thing although it tends to more often than not just remind me that I am, not, in fact, in Hawaii and then life just starts to suck. But also because they will sometimes eat caulerpa and other macros and I needed some help keeping that stuff at bay. But alas, it turns out that "sometimes" means the same as "sometimes not" and guess which category mine fell into? Not the caulerpa eating helpful category, but the "Your Feng Shui is all wrong, here let me help" kind of helpful category. Stupid urchins.

Hey Tony do you like Hawaii?

I don't know if I'm a bad person or not, but I love laughing at your expense tony ha

not all the time but its entertaining

my rock urchin lives in the sump as well. Fat little bugger

Hah, thanks for the input guys!

My tank had some caulerpa when it was initially setup, but I removed them all by hand long before this one was introduced into the tank, so I have no idea whether mine eats or not and I only see them at night...but I supposed all urchins are beneficial one way or another:mrgreen: only got worried cuz it grew so much so fast.

I had to draw it out with measurement cuz I couldn't remove it from the tank =D and there was nothing to compare to anyway =P

Mine stripped a whole tonne of nice thick coraline off my established rocks.... so be weary!