I looked up teh urchins on the web. They look more like diadema urchins.
The spines are relatively short with a purple hue. It looked something like
a reef urchin, but it did not have the round white bad at the base of each
stem. I have been wondering why I have been losing coraline, I assume these
guys are not helping matters.
"Pszemol" wrote in message
...
"david" wrote in message
ink.net...
I bought live rock for my new tank about 1.5 months ago. (Carribean
Aquacultured) I noticed a couple of urchins came with the live rocks,
but
now I have seven. Are these creatures a pest I need to worry about? I
read
they eat algae which is fine by me, but do they do any damage to other
reef
creatures?

What urchins are they? Diadema? Tuxedo urchin?
The second is not growing large and is recommended for a larger reef tank.

It is rather unlikely they spawn in your tank... and if so,
there is even more unlikely their larvae survive pumps/filters.
Most likely, tiny ones come with the rock and you did not noticed them.
Now, when they grown, they are more visible :-)