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Re: Lead, an Important Nutrient

Jared wrote:
I suspect the "lead" is a translation error. While we are on the subject of
essential nutrients, I found it curious that Flourish liquid was one of the
only fertilizers to contain (or at least declare) Nickel, needed for the
enzyme urease. It's one of the 17 nutrients listed, for example, in Diana
Walstad's book. I was curious about some of the other elements present in
very small amounts in Flourish:


I thought perhaps that SeaChem was just being scrupulous and was reporting
contaminants, but Greg Morin replied to my query:

<< They are required. Everything we add is for a reason and not as a
contaminant. I know that the vanadium is also utilized in some enzymes, the
others I don't recall offhand as to their specific use... >>

Why then are these not mentioned in our aquatic-plant references if they
are physiological requirements? Are any, like boron, specific for aquatic
(and not terrestial) plants? Also, if they are missing from other
commercial fertilizers, I assume that our water supplies provide them.

Several others have addressed the "Lead" issue, so I think that it is safe
to say that this was probably a translation problem or a mistake - lead is
not, as far as I can find, required or even desired by plants for anything.

Most lists of "essential nutrients" for plants contain either 16 or 17
elements. However there are also several elements which may be essential for
some (but not all) plants and others which may be beneficial (again, for
some, but not necessarily all plants). But the actual "number" depends to a
large extent upon how you count the elements.

In order for an element to be considered "essential", it should meet the
criteria proposed in 1939 by Arnon and Stout. These are:
1. A plant must be unable to complete its life cycle in the absence of the
mineral element.
2. The function of the element must not be replaceable by another mineral
3. The element must be directly involved in plant metabolism.

"Beneficial" elements are those that can compensate for toxic effects of
other elements or may replace mineral nutrients in some other less specific
function such as the maintenance of osmotic pressure.

The "essential" macroelements (those required in large quantities) are
usually divided into non-mineral (supplied by air and water) and mineral.
Micronutrients are those mineral elements which are only required in trace
(very small) amounts.

Essential Non-mineral Nutrients:
1.  Carbon
2.  Hydrogen
3.  Oxygen

Essential Mineral Macronutrients:
4.  Nitrogen
5.  Phosphorous
6.  Potassium
7.  Calcium
8.  Magnesium
9.  Sulfur

Essential Mineral Micronutrients:
10. Boron
11. Chlorine
12. Copper
13. Iron
14. Manganese
15. Sodium
16. Zinc
17. Molybdenum
18. Nickel
(Nickel has been added to the list of "essentials" relatively recently and
may not be required for all plants.)

Beneficial Mineral Elements (probably required in VERY small amounts, if at
18. Cobalt
19. Silicon
20. Aluminium
21. Cobalt
22. Selenium
23. Platinum
24. Vandium
(This list comes from http://www.hydrospecial.com/Nutrition.htm, so shoot
them, not me, if you disagree with the inclusion of any particular element
on the list.)

It would appear that recent advances and on-going research in plant
nutrition are having the effect of showing that the list of both "essential"
and "beneficial" elements is only going to get longer, not shorter, and it
is nice to see that at least one commercial manufacturer is keeping up with
new advances in the field and passing on the (possible) benefits to the
hobbyist in their products.

Remember as well that elements like Iodine and Bromine might be helpful to
MARINE organisms.

Zack wrote:
Regarding these more obscure micronutrients that are being discussed, I
would appreciate knowing if people have seen any evidence of a need for them
in their planted aquariums.

    Paul Krombholz just mentioned in a posting that he uses rain water, and
as I remember, James Purchase uses RO.  I wonder if they, and others using
these purer waters find it necessary to add any of these other elements?
Have they used products like Flourish, or Kent's Discus Essential ( which
also contains a long list of elements)?  Do they have substrates- ie: soil,
that might be a source?

I _used_ to use RO water in my main tank, fearing that (possible) pollution
from my tap water (which comes from Lake Ontario after passing thru Love
Canal) might have been the cause of my ongoing battle with algae. But RO is
a pain and I've since learned to both trust the water supply (silly fool
that I am, given recent events in Ontario) and the real cause for my algae
problem (overdone substrate). So now I use Toronto tapwater.

I use a variety of products in my tanks: Seachem's entire line, Aqualine
Buschke products, Dupla, DIY PMDD, Jobe's Spikes, you name it, my "aquarium
closet" probably has a bottle or two of it in there. I also tend to "flush"
my tanks on a semi-regular basis (i.e. several massive water changes spaced
closely together) in an effort to make sure that anything that is either
missing or in excess is either replaced or flushed out. I don't run heavily
fertilized tanks any more - they are all on pretty slim diets. But the
plants grow, and don't seem to be experiencing any problems.

I don't see, nor could I tell, if any of the "obscure" beneficial elements
is either lacking or in excess in my tanks - and neither, I'd venture to
guess, could any other hobbyist. These things, if they are doing anything at
all, are probably present as "contaminants" either in my water supply or in
my substrates or the fish food I use. I don't sweat them, and I don't think
that anyone else need worry about them either. Aquarists do not, as a rule,
operate their tanks in a manner, nor have access to the analytical equipment
necessary to determine the presence or absence of elements which may only be
needed on a parts per billion basis._Anyone_ who tells you that they can
determine that your tank need more vandium (for example) from looking at it
(or photos of it) is blowing smoke.

James Purchase