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Re: Questions about PMDD
"Michael Bartnik" <rev_grover at hotmail_com> wrote a while ago:
> I have a few questions about PMDD that I hope someone could answer. Let
> me start out by stating that I won't argue about whether PMDD method
> works. It clearly does. I am having trouble determining proper dosing.
> If I understand correctly the best method is to measure the iron content
> of the water and dose enough PMDD to keep iron levels at .1 ppm. I'm
> using terralit as a substrate additive and have never had insufficient
> iron level in my tank <.1 ppm (also no signs of iron deficiency in my
> plants). In addition recent posts have been pointing out that the test
> kits used are not measuring chelated iron. The forms of iron
> registering on the tests are not the ones being used by plants.
> This leads me to think that I should be using another method to
> determine dose size. Plant condition might be a option but I have never
> observed an overt element deficiency in my plants. Just slow growth in
> some species, rising nitrate levels, and outbreaks of algae. Is there
> another trace element I can measure effectively to determine PMDD dose
> size. Ideally it would be something used by the plants readily and
> quickly maybe sulphur (.05% to 1.5% concentration in dry weight if
> plant) or manganese (.0005% to .15% concentration in dry weight of
> plants). How quickly is sulphur and manganese used in plants, and can
> they be measured effectively.
> Any input anyone can give would be greatly appreciated.
I suggest that you stop adding the trace nutrients in solution and
supply them instead by the substrate. Then just calculate the dosage of
minerals to achieve 10 ppm of NO3, K and Mg based on additions with the
water changed at water change time. Details are on my webpage
Steve Pushak Vancouver, BC, CANADA
Visit "Steve's Aquatic Page" http://home.infinet.net/teban/
for LOTS of pics, tips and links for aquatic gardening!!!