Sea Urchins

So, does anyone have strong feelings about sea urchins?  Good, bad, or indifferent?  Tell me the scoop! 

I have one.  They can be VERY destructive to your rock structure.  They get between two rocks then expand knocking the rocks over.  They are suprisingly strong.  I ended up moving mine to my refugium where he has done very well.

Renee,

I added a pencil urchin several months ago and removed it a couple months ago. He at coralline like crazy. Faster than my tank could recover it. He now lives in 29 gallon tank in the basement with a bunch of live rock. He is a pretty good grazer, but I wouldn't add another to my display tank.

I have 2 green/white pin cushion urchins in my 90 gallon.  They definetly have pros/cons to them.  Pros: I think they are very cool to look at and watch them move around while they put shells onto their back.  I've even seen them pick up a hermit crab with the little hermits dangling out the side.  They eat coralline algae, in which I think helps my live rock "breathe."  They are very sure footed.  There definetly the best grazers in my tank.  I have never seen them bother any of my corals and I have a mixed reef.  Cons:  They eat coralline algae, but my coralline is able to keep up with them.  They knock over rocks/corals that are not securely fastened.  I have now gotten to know exactly what I can and can't do as far as placing rocks and attaching frags so that they no longer tip anything over for the most part.  Overall I think they are just a cool animal to have. 

Hmm.... so 2 of you that have posted have seen my aquascaping.  It's very open - lots of caves, but the LR is not glued or permanently connected in any way.  But I have so much corraline!   Anybody want to have a scraping party with me?  I scraped it for all 4 days last weekend (Yeah, it sounds pathetic.  But I didn't have a single other thing to do.)  and it's still really thick in a 5 inch band along the bottom.  I don't mind something munching a coral once in a while, because I would hope they would go for the easy crunchies along the acrylic wall.   Hmmm...

Renee, You should try one and see if you like it. It's easy to remove. The Pencil urchins seem to be more destructive and the collector urchins are the most fun.

Start by putting it on the glass to help with coralline removal. It makes neat scraping patterns on the glass with its 5 teeth.

Will their teeth scratch acrylic?  That was a serious question, right?

yes that was a serious question.  If a critter has a mouth and teeth that can crunch up coralline algae they might be able to scratch acrylic too (as they eat algae off the acrylic).  But it is a question, cause I don't know?

So possibly a collector urchin, and we're not sure if they could harm acrylic.  And it appears that Adam has a crab & urchin that are captured and separate from the corals (?)