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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!!!