Common reef urchin?

[softiegirl]

Ok. Cant get any response on this on my other forum, maybe you can help! About 6 months ago i noticed a nickel sized hitch-hiker in the tank. I identified it online as a reef urchin. Not quite a long spine, more short and squat with purple spikes. Pretty neat looking guy, only comes out at nite. He is about 4 inches around right now but can fit himself into some pretty tight spots! Was looking in the tank the other nite and lo and behold... another one! teeny like the first. Havent put any new live rock in for quite awhile. Do they reproduce asexually? Are they bad for my system? Doesnt seem to do much harm except knock stuff over at nite.... any input?
here's his mug shot!

 

[roshi719]

From my experience they just eat all your coraline and bulldoze everything in their path. Other than that they are harmless.

 

[thincat]

Looks like a "pencil urchin". Like roshi said the only down side to them is that they knock things over. If you can put up with it rearranging your DT, then I would not worry about it. Some urchins can reproduce by segments, I'm not sure about the pencil urchins doing that.

 

[softiegirl]

well the pencil urchin has blunt tips. his are very pointy. and at the base of the tip on his body is a white ring on the black body. I will most likely take him out when he gets to be too clumsy, ive got so much coraline it would take him a year to eat it. But i was really puzzled when the newest one turned up! :squigglemouth:

 

[roshi719]

I believe it could be a shortspine urchin as opposed to a pencil urchin. As far as where the little came from... The world may never know.

 

[cparka23]

That isa pencil urchin. I have had two and their tips were as 'pointy' as those in your photo.

As for your other questions, they are broadcast spawners -- not capable of asexual reproduction. I've heard of them scuffing the surface of acrylic tanks with their 'teeth.'

 

[mevstheworld]

I have the exact same thing. He eats coralline like a vacuum and ornamental algae. I had 2 large pieces of spatula algae and he devastated them both overnight. He now resides in my sump