How big will my sea urchins get? (w/ pic)

[djmpj2]

We have 2 sea urchins that came with our Live Rock. My son is very curious to know how big they will get. They were the size of a spec when we got them just 6 months ago. Now one is about 4.5 inces and the other is slightly smaller.

Here is a pic:
http://jeffries.smugmug.com/gallery/646323/1/30994288

Thanks
DJ

 

[Fluff]

That's a common purple urchin. I have one that's about three years old. They grow fast to about 4" across from tip of spine, to tip of spine.

 

[revhtree]

Great tank!

 

[djmpj2]

Rev - Thank you so much!!

Fluff - Thanks for the info. I guess mine is pretty much full grown then. Good to know.

D

 

[Kam]

Has anyone had these reproduce on them?? I think I have.

I had 3 of these urchins as hitchhickers on LR that I got back in April. The largest was about the size of a quarter, the other two smaller and smaller again (kids named them small, medium and large). I recently found 3 new very small urchins. I am trying to figure out if they reproduced or if these other three were there all along and just too small to notice. The interesting thing is that the 3 new ones all appeared on the same small chuck of LR out of over 80 lbs, which leads me to think they were born there vs hiding the whole time.