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Re: Aquatic Plants Digest V3 #1238

On Fri, 27 Aug 1999, Bryan Bankhead wrote:

> 	The Sera Test doesn't work with chelated iron supplements. The iron in
> Sera is a the form of Iron Chloride and the EDTA is separate, rather
> than using an iron EDTA salt. How this relates to how the test works is
> anybodys guess.

The iron is chelated.  When you combine EDTA with a solution of a soluble
iron salt like iron chloride, the iron is chelated by the EDTA and the
countering ion (chloride in this case) is balanced by a cation (probably
sodium) released from the EDTA.  Different chelated iron mixes use iron
from different soluble salts.  I think Tetra's Florapride (for instance)
uses iron sulfate.

If it took an entire 100 ml bottle of Sera fertilizer to give 1 mg/l of
iron, then the fertilizer would be rather weak.  Florapride is 0.15% iron
chelated with EDTA and 100ml of that in 15 gallons of water would give an
iron concentration of over 2.6 mg/l.  Hagen's Plantgro is 0.085% iron and
100 ml of that in 15 gallons of water would give 1.5 mg/l.

My only point all along has been that you probably added more fertilizer
than you needed, and I think your posts are showing that.  Probably you
don't have anything in the tank that will be particularly sensitive to the
iron or whatever else is in the fertilizer, so you aren't likely to see
any toxicity impacts.  It does mean that you'll have to replace your
fertilizer supply quite a bit earlier than you otherwise would need to.

Roger Miller