urchin owners

[buzzer]

I have read recently in an article that urchins will make a quick meal of a cuttle bone, have any of you tried this and if so is this a normal cuttlefish bone from the local pet store and do you just place in aquarium.
The benefits of the cuttle bone is to provide the urchin with the calcium that they require.
Also how often would you feed such an item.

[Ben CC]

Never heard of the cuttle bone thing, but my urchins seem to be happy eating the algae/etc. in my tank and if they do need a source of calcium, isn't coralline algae calcium-based?

[sjvl51]

I've never heard this either. My urchin is happy with what it gets in the tank.

Vickie

[rottn]

I've never heard of it either. Almost sounds like a wive's tail to me...

How would you secure a cuttle bone? Aren't they pretty light? I can see it floating away. Unless you attached it with an elastic to a small rock or something.

I dunno. I still think it sounds kinda way out there though. Critters that require calcium, such as urchins, snails, crabs, clams, sps corals, etc. get their calcium through the levels found in the water itself. SW naturally has levels of calcium in it (along with many other trace elements), but the more critters you have that require calcium, the more you have to watch you calcium levels, and possibly add calcium via kalk/calcium reactor/B-Ionic/etc.

I just can't imagine my urchins (or snails, or any of my "calcium requiring" critters) actually eating a cuttle bone.

I could be completely wrong of course, but it just sounds very odd to me.

JMHO

[buzzer]

Thanks for the replies.
I have typed a small exerpt from the article which was found in MARINE WORLD june july 2003 edition.
A grazing urchin may remove large amounts of calcareous algae that in most aquaria will not be able to recover quickly enough to withstand the grazing pressure.
The desire of an urchin for calcium carbonate is such that you can supplement their uptake with pieces of cuttlebone, which will be grazed to nothing in no time at all.
This article was written by a guy called Tristan Lougher
This guy is English so am not sure if you have eve heard of him but over hear he has a good reputation.
I too have never heard of this before but am intrigued as to whether it is a good idea.

[Randy Holmes-Farley]

I do not know whether an urchin would eat a bone, but I discuss sea urchin usage of calcium carbonate in this article:

Sea Urchins: A Chemical Perspective
http://reefkeeping.com/issues/2004-08/rhf/index.htm

a section from it:

"Sea Urchin Spine Formation: Uptake of Calcium and Carbonate

Sea urchins can take calcium and alkalinity directly from the water column to deposit calcite to form spines. This has been demonstrated by the fact that some (e.g., Strongylocentrotus purpuratus) have been shown to be able to take calcium from solution and calcify even when kept under starvation conditions, although the calcification rate was slower than under fed conditions.5

At least two species, however, have been shown to have some propensity to consume solid calcium carbonate that may be dissolved by the lower pH in their guts and released to the organism to provide the building blocks for calcification, sort of like miniature CaCO3 reactors.6 In these experiments, Diadema setosum and Echinometra sp. were shown to prefer artificial foods with powdered calcite added over the same foods with no calcite. Many urchins might similarly obtain calcium and carbonate ("alkalinity") from the calcareous algae and other bits of calcium carbonate that they consume. [As an interesting aside, it has been claimed that many calcareous algae deposit CaCO3 in an effort to make themselves less palatable to fish.7 In the case of sea urchins, this strategy appears to backfire.]

Will urchins significantly deplete calcium and alkalinity in a reef aquarium? Probably not very much relative to other calcifying organisms, but in a new aquarium in which coralline algae and corals may be calcifying slowly, this relatively low depletion rate may be an appreciable part of the total. When I first set up my reef aquarium, I used wild Florida live rock that contained quite a load of sea urchin hitchhikers. More than 30 rock-boring urchins (Echinometra lucunter) were present, and they grew very rapidly for a year or so, before dwindling. During that time, coralline algae grew poorly (even in areas not browsed by the urchins) and I had few rapidly calcifying corals. Consequently, while I did not realize it at the time, some of the limewater that I was adding may have been ending up in the urchins. As an aside, studies have shown that moderate grazing by sea urchins can increase the spread of coralline algae from the chips that are released. However, in a finite space like a reef aquarium, heavy sea urchin grazing may overwhelm the growth of coralline algae."

[buzzer]

Nice informative answer Randy...thanks.

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.