Urchin questions!

[SF_Ice]

Recently picked up a long spine, blue spot urchin. In the last few days it has done an amazing job eating algae. It cruises all over the tank and to my surprises moves pretty quickly when it wants to.

1. It has a "Bulb" on the top center of the body that seems to grow and shrink periodically.
2. It loves going over, through,and around my Zoas, will the spines sting and kill the zoas?

I think it was a slightly impulsive purchase as I've always wanted one and they seem to be relatively easy to care for, but if need be I can banish to the sump vs the expense of losing my zoas, while i search for a new home for it. Let me know what you all think!!

Thanks in advance

 

[lapin]

My long spined never bothered corals. My pencil can mow over them and leave nothing but bare rock behind.

 

[S2G]

They knock over plugs but you should be ok.

 

[cristata.reef]

Assuming the urchin you have is a Diadema, Echinothrix, or some other related species, the bulb is part of its body, simply called the anal cone (trust me don't look it up without adding the word "urchin"). It's function is not properly understood and may differ by species (see http://echinoblog.blogspot.com/2012/05/anal-cones-diadematid-sea-urchin.html).

 

[stanleo]

I've had mine for months and it doesn't hurt anything. It's pretty cool. I feed the algae to the tang an hour or so before lights out so the urchin can get some of it when the lights go out. I don't think I have enough algae in the tank for him to survive so he needs supplemental feeding. I also throw an algae wafer in at night for him.