[APD] Re:Barr Method Question

[Paul Krombholz <krombhol at teclink_net>]

  Dale wrote:
> .....Even with 50 % weekly water changes and assuming no plant 
> up-take (bad assumption I know), the nutrient levels would continue 
> to rise in the tank.........

The nutrient level does not build up indefinitely.  Assuming you add 
nitrate to initially give a value of 10 ppm, do a 50% water change, 
then add the same amount of nitrate,  and that the plants don't 
remove any, the level in the tank will  level off at 20 ppm.  If you 
do as above, but with 75% water changes, the content will level off 
at 13.333 ppm.  With 25% water changes you level off at 40 ppm.  The 
general formula appears to be that you level off at the initial 
concentration times 1/(% water change)

--
Paul Krombholz in rainy central Mississippi---lots of rain!
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