Posts Tagged ‘strontium’


Thursday, July 22nd, 2010

It is time for my usual and periodic rant about the idiocies apparent in the coral reef aquarium hobby.  The particular thorn-in-the-paw that has set me off this time is one of the usual ones that have been beating around the scientific blogosphere over the last year or so; specifically, the lack of scientific literacy amongst the public – or in my case, the particular subset of the public that I sometimes interact with – the average aquarists I try to advise, or work with, or write for.  I have to throw in a caveat here; there are a fair number of very good aquarists, who can actually look up articles, and act upon what they read.  However, they are a small subset of the total number, and are the exceptions rather than the rule.  If you count yourself amongst this group, and have actually read something in the peer-reviewed literature, I hope the rest of this diatribe does not offend you.

I suppose I may be guilty of one on the mistakes I warn my readers about, that being making unwarranted generalizations.  Still…  It seems like trying to introduce common good husbandry based on scientific knowledge practices to the majorit of this group of folks is a useless task.

Nothing I propose is based on anything other than scientifically determined facts and good common sense, buttressed by those facts.  Most of the time following the suggestions would save a lot of money.  In all cases, it would result in healthier, longer-lived animals.  And after 15 years of doing this, I think I could count on the fingers of one hand the number of people who regularly correspond with me who seem to “get it.”  And, even though there are probably more, the fact of the low numbers is damned discouraging.

 The Aquarium Advice Form Of Gresham’s Law

 Gresham’s law in economics states that “Bad money drives out good.”  Basically, if two types of currency circulate simultaneously, and their exchange rates are governed by law, the artificially overvalued money tends to drive the other, artificially undervalued, or “the more valuable or good,” money out of circulation.  In the aquarium hobby world, it is the artificially overvalued advice, mostly advertisments, but some other advice as well, drives out or submerges the artificially undervalued advice, that based on scientific evidence.

One probably shouldn’t take this analogy too far, but it works pretty well on the short run.  Advice that is overvalued is that which is continually trumpeted by advertisements.  This advice is everywhere in short bursts, it is easily learned, and it is often repeated by people who don’t know how to test or evaluate it or probably more correctly, don’t care to test or evaluate it.  As we all know, continual exposure to a patent falsehood claimed to be true will result in that falsehood being accepted as the truth by the majority of the audience exposed to the repeated message.  This was discovered and explicitly stated by Joseph Goebbels, and has been exploited by every propagandist since then.  Of course, it was probably intuited by every natural-born scam artist since the first travelling caveman sold defective obsidian on his way through an ancient valley.  And it continues to be inuited today, and exists well in the advertisements aimed at aquarium hobbyists. 

The undervalued advice in my example, scientifically determined knowledge, requires the recipients to think about it and to implement it often in the face of an overwhelming amount of contrary advice.  That is hard to do, particularly when the recipients are today’s typical Americans who have never had any training in how to evaluate ideas or claims, and whose knowledge of science and the scientific method have been formed by shows such The X-Files

There are numerous examples of how idiotic advice seems to rise to the top in the aquarium hobby, but my favorites for today are the use of strontium and iodine as additives in aquaria.

Strontium is a known coral poison affecting calcium metabolism.  It has been demonstrated to reduce calcium transport across the coral’s surface membranes, and that is definitely not a good thing.  Fortunately, it doesn’t kill corals outright, and the the concentrations found in natural sea water, evolution has given corals the ability to detoxify it.  Still, adding it to an aquarium, to “boost” coral growth is not a really sterling example of the intelligence of the average reef aquarist.

Then there is the addition of iodine.  This material, often added in one of the many formulations called Lugol’s solution, is an essential material, in very small amounts.  The amounts necessary in a reef aquarium are so tiny as to be effectively unmeasurable.  Excess amounts of iodine are amazingly lethal.  Like many budding scientists who worked in freshwater systems, I learned about Lugol’s solution in my limnology classes, where it was used as a preservative. 

Yeah, that’s right.  A preservative, a material used to kill organisms and make them so toxic that nothing could eat them. 

Good stuff, to be adding to one’s aquarium, to be sure.  Especially as it is impossible to hobbyists test for iodine in aquaria as it has exceptionally complicated chemistry and no cheap test kits are available.  But that doesn’t matter, as you see, we all know that iodine is essential for crustaceans.  Particularly because it is necessary for crustacean molting.

Necessary for molting in crustaceans… You know, crustacean molting has been investigated in great detail by arthrophysiologists for as long as there have been scientific arthropod studies.  This is well over 100 years, and there is an amazing body of literature about the chemical aspects of molting in crustaceans.  Litereally, there are thousands of articles.  Turning to the Advanced Search in Google Scholar to get an estimate of the number of articles turned 11,800 hits, about 210 of these articles contain a mention of iodine.  A few of those discussing iodine inside the molting fluid and in the water outside the animal, along with all other ions the researcher could measure, but most of the mentions of iodine were as a component of various testing chemicals, not normally found in the animal but used as a reagent to indicate some other factor.

The sum total of articles mentioning iodine in any of its many forms as being necessary for molting was…   

Wait for it…


One would think that if iodine were necessary for crustacean molting, there would be a plethora of articles describing its action.  There are for every other necessary chemical, such as 3,820 for phosphate, 3,210 for copper, 2,680 for iron, 2,520 sulfate, 4,080 for calcium.  Iodine zip…   Search engines turn up a lot of false positives, and depending on how one queries for iodine, hits can be found.  But, when those articles are examined, NONE of them discuss iodine as a necessity for molting. 

 Negative evidence is, of course, difficult to deal with.  The old saw, “Absence of evidence is not evidence of absence,” remains as sharp as ever.  Still, one would think that somewhere along the line, if iodine were a requirement for arthropod molting, some researcher over the last century would have found it.

Anecdotal stories from aquarists seems to indicate that iodine supplementation seems to cause some changes in molting.  My suspicion, my very strong suspicion, is that iodine poisons the molting process and causes premature molting.  Repeated iodine forced -molts result in premature death.   At the very least.  Now, I would love to be shown to be wrong.  But, I am not going to hold my breath waiting for such evidence to appear.

Below are some references about strontium in corals, they are all worth reading.  It is particularly enlightening to read the first two, and then the rest.  The first one tells how increasing strontium causes increased growth in corals.  The second one tells how that growth was an artifact of the experimental system.  The first one is used by incompetent aquarists to support their supposition about adding strontium.  These aquarists are incompetent because they didn’t read the next article.  And the subsequent ones.  

Of course if you want to read an article in the scientific peer-reviewed literature detailing with the necessity of iodine in crustacean molting.  You will have to find it.  I couldn’t.  

On the other hand, the aquarium version of Gresham’s law is alive and well, just check out any aquarium vendor and their online advice about iodine and strontium.

More later…


Strontium References:

Swart, P. K. 1980. The effect of seawater chemistry on the growth rates of some scleractinian corals. In: R. Tardent and P. Tardent (Editors). Developmental and Cellular Biology of Coelenterates. Proceedings of the Fourth International Coelenterate Symposium. Interlaken. pp. 203-208.
Swart, P. K. 1981. The strontium, magnesium and sodium composition of recent scleractinian coral skeletons as standards for paleoenvironmental analysis. Palaeogeogrraphy, Paleoclimatololy, Paleoecology. 34:115-136.

Chalker, B. E. 1981. Skeletogenesis in scleractinian corals: the transport and deposition of strontium and calcium. In: S.C. Skoryna (Ed.) Handbook of Stable Strontium. Plenum Press. New York, pp. 47 63.
Ip, Y. K. and P. Krishnaveni. 1991. Incorporation of strontium (90Sr2+) into the skeleton of the hermatypic coral Galaxea fascicularis. Journal of Experimental Zoology. 258:273-276.
Wright, O. P. and A. T. Marshall. 1991. Calcium transport across the isolated oral epithelium of scleractinian corals. Coral Reefs. 10:37-40.
Greegor, R. B., N. E. Pingitore, Jr. and F. W. Lytle. 1997. Strontianite in coral skeletal aragonite. Science. 275:1452-1454.