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Re: iron levels

> From: "Eric Wahlig" <ewahlig at earthlink_net>
> Subject: Re: iron levels
> I said in a recent post: "Well, I have a very good iron test kit and I was
> consistently measuring
> about 0.03 mg/L Fe in three 20 gallon tanks."
> I should say that, although this test kit is of high quality, it measures
> the total concentration of iron by converting any ferric iron present into
> the ferrous state. So, it's impossible for me to measure the concentration
> of (plant usable form) ferrous iron that is present in the tank at any time
> with this test.

	There have been discussions of this before.  As far as I know,
plants have no problem using ferric iron.  In fact, NaFeEDTA (Fe III) is
used as an iron supplement in agriculture.  I seem to recall Dave
Huebert confirng this quite a while ago.  The problem with iron III
in an aquarium is that if it isn't chelated, the Fe+++ ion is very
readily hydrolysed, giving the insoluble oxohyroxide, which ends up in
the filter.  If it _is_ chelated, it doesn't matter which oxidation
state it's in.  If plants used ferric iron only, I can't see that much
would grow anywhere - ever.


Paul Sears
psears_at_nrn1.nrcan.gc.ca, 613-996-4171, facsimile / tÚlÚcopieur 613-996-9400
Natural Resources Canada, 1, Haanel Drive, Nepean, Ontario K1A 1M1
Ressources naturelles Canada, 1, Haanel Drive, Nepean, Ontario K1A 1M1
Government of Canada / Gouvernement du Canada