To: aquatic-plants at actwin_com (Receipt Notification Requested)
From: Christopher.Holloway at hr-m_b-m.defence.gov.au
Date: 24 Oct 96 10:59:47 +0000
Delivery-Date: 24 Oct 96 10:59:47 +0000
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X400-Originator: Christopher.Holloway at hr-m_b-m.defence.gov.au
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the PMDD recipe is at
and is attached to a document on algae control as an appendix.
I have been trying to get a hydroponics shop to mix me up a batch. I
have also been talking to Paul Sears and Pat Bowerman about the actual
chemistry mixture, and I have also been talking to James Wong. Thanks
to all three for their help and their patience.
Not being a chemist I have found the PMDD recipe to be fairly
confusing. It transpires from several exchanges that the percentages
of trace metals listed as part of the PMDD recipe do not refer to the
chelated metal complexes themselves; rather, I THINK they refer to the
amount of metal delivered by the chelated complex once the complex is
'active' in solution.
This is to say that if you get a TE mix recipe that calls for 7% Fe
(as the PMDD recipe does), and you make up a mix that contains 7% Fe
chelate, you don't actually end up with 7% Fe in the water and
available to the plants. You actually end up with a considerable
anmount less - as Pat explained it, you end up with about 1.5% Fe
available to the plants.
I find this very confusing, and I'm still not sure that I have this
right. I also suspect that I'm not the only one in this situation.
Perhaps someone could help us spuds out a bit with a detailed
explanation of how to explain this arrangement to a hydroponics shop.
On a slightly different note I found at
a recipe provided by Shiao Y. Wang in 1995 for a trace element mix
which apparently is a plant tissue culture media. It's comprised of
EDTA sodium ferric salt 40g
per litre (of distilled water?). The dosage rate is given as 30ml per
30 gallons of water in a 75 gallon tank but I would assume this would
need to be varied to suit individual tank conditions.
Personally I find this recipe great deal easier to get my head around.
I also imagine that it will be easier to ask a hydroponics shop to mix
up (say) half a kilo of this stuff, keeping the proportions even. I
have been told that these things should be readily available at most
chemical supply shops and, by multiplying the amounts given above by
(say) 100, the average chemically-illiterate punter like myself should
be able to put the mix together.
Any comments would be extremely welcome.