Reefing with Royal Urchins

This royal urchin is the latest addition to my reef aquarium and truly fascinating. For the past month I have watched it methodically grooming my rocks. It seems to have favorite spots that it visits daily. This intrigues me as apparently Sea Urchins do not have brains but a 'nerve ring' near their mouths. What accounts for memory? How does my royal urchin end up finding that same spot shown here every day? I don't know. But that little bit of Caulerpa nearby doesn't worry me like it used too.



My urchin eats just a little bit more every day of these caulerpa strands that found their way into my display tank after I shut down my external refugium in a child-proofing frenzy. This behavior is welcome and also intriguing. It almost seems to display discipline - leaving just a bit for tomorrow's feeding. Yet is doesn't have a brain. How does this happen? I am mesmerized as soon as I get home from work, asking the same questions over and over.

The urchin gets around on tube feet. These feet will flap around in the current when loose. This is a good sign to note when considering purchasing a royal urchin. If you see one at the LFS and it's all spines and not moving, I'd pass on it. These inverts don't seem to travel well or, at the very least, require decent acclimation procedures.

The spines are principally for defense from what I can tell. My cleaner shrimp jumped on it one day and the urchin went stiff with spines straight out. I found this amusing as that cleaner shrimp tends to drive me nuts too when trying to feed corals.

Another oddity with royal urchins is that they are truly butt-heads with their anus on top and mouth on bottom. Occasional scat storms occur that erupt from the top of them.

Their mouths with their five symmetrical teeth are equally fascinating to watch open and close when on the glass. These are strong teeth too. If you rocks need a shave there may be nothing better around. A royal will give them a #1 clipper cut often going all the way to the rock.

Are they reef-safe? Yes.

My urchin has been deftly going around my SPS, displaying truly amazing vertical climbing skills. It appears only interested in algae. All types of algae. Including coraline which will bum some people out. But I think the benefits of it grazing down the nasty stuff and keeping the tank tidy outweigh this concern. Also it really hasn't made a dent in my coraline at all. Perhaps it will in time, but it will grow back. And its growth rate may exceed that which is lost to the urchin.

There are some things to be aware of.

If your rocks are balanced like a house-of-cards, an urchin will ultimately make you make a better effort to strengthen the aqua-scape as it will knock the loose ones down eventually.

Also if your frags are not glued down well, a urchin will let you know too.

These are things I was aware of getting this one and so far so good for me, but I do recall from tanks past having these issues.

Algaes

Royal urchins will munch on most all algaes I've noticed. Most micros like the film on the glass and greens on the rock… all the macros in my tank from caulerpa to halimeda. I wish it would mow them down faster but it is very methodic. It seems to start on one end of the rock and make its way like a glacier leaving white in its path and slowly encroaching on the big macro stuff, edging into it a bit more each day.

My urchin does not appear to like the taste of the truly slimely cyano algae that I have in spots since my refugium came down. It has hit it here and there, but it seems to prefer the other algaes. I hold hope that it will finish it off in time.

If not, I am literally hours away from obtaining some chaeto from a fellow 3reefer and starting a new sump refugium.

But regardless this urchin stays as part of my clean up crew. With a shallow tank and a halide lamp, I consider him critical and wonder why I didn't get him earlier. Perhaps you will too.


matt


More on the anatomy of a sea urchin:
http://www.stanford.edu/~seastar/VirtualUrchin/urchinanatomy.swf
SUE - ANATOMY & PHYSIOLOGY

 

Wow, beautiful add Matt.

 

Sweet add Matt! I've always wanted one,but even reef safe,i'm not sure i'm comfortable with all those spines around my softies and lps.But man,I really stare at them at the stores.Seen one a while back (I believe it was called a halloween urchin) and it was all I could do not to bring it home,lol.

 

Nice job! I have a small long spine urchin and he's a good grazed but not as good as I hoped. I really enjoy the "scat storm", too. Does that make him a ****head?

 

With regard to finding the same spots to reside in, I think they must lay down some type of pheromones (something similar) trail. Sea Urchins, Abalone, Limpets and some snails seem to find their way back to identical spots. I have seen this in the wild with Chitons and some Star fish and always wondered why, but never invested any time into the answer.

I love Urchins but my tanks have been too small with too many loose frags to tumble.

Thank you for sharing.

 

Nice write up Matt. Having kept several type of urchins I agree these are the best. They eat very little coralline off the rocks compared to film and hair algae.

I suggest staying away from short and long-spined urchins for the coralline eating issue, unles of course thats not an issue for you!

 

Nice add Matt - and nice write up! I love my royal urchin - such a fabulous addition to my tank.

Glad you're enjoying your little guy so much!

 

First, nice write up Matt. I myself keep a Blue Tuxedo Urchin, and have witnessed the same behavior. He's also likely the best CUC member I have. I'm really tempted to get 1-2 more, as one of these guys doesn't cover a whole lot of real-estate in a timely manner.

Second, it appear as though the species you have is a Tripneustes gratilla. This is the species which is commonly labeled as "Halloween Urchin" or "Orange & Black Urchin". Now, I can't say as though I've ever heard of any accounts of this species causing harm to people or tanks, but I will say Bob Fenner is rather opposed to them. This steered me away from this particular species in the past.

Via Web Wet Media:

 

Hey thanks for info evolved. That ID seems accurate on the looks, although I have touched it a bit to no effects. I might avoid that now. It's certainly touched my shrimp and corals without issue.

I'm glad you posted that bit about adorning itself with bits of algae. I love when they put on a 'hat' ( or is it pants? ) and walk around.


Thanks all for sharing your experiences too.

matt

 

Thanks for info Corailine - that is a really interesting. That could be true I bet.