[APD] CO2 Measurement Method

[Vaughn Hopkins <hoppycalif at yahoo_com>]

I have a cork wall in my 29 gallon tank.  I also have been measuring 
150 - 250 ppm CO2 using PH/KH table.  Being somewhat dim witted it has 
taken far too long for me to connect those two facts.  Apparently cork 
leaches tannins into the water which drops the PH a bit, making the 
PH/KH/CO2 table inaccurate.  Today I checked a water sample taken from 
the tank last night and allowed to sit over night vs. one taken this 
morning.  Last nights sample had KH of 9 degrees, PH of 7.0 - 27 ppm 
CO2.  Todays fresh sample had KH of 9 degrees and PH of 6.2 - 170 ppm 
CO2.    I think this strongly indicates that the cork is fouling up the 
CO2 measurement.   But, the .8 drop in PH should mean my actual CO2 is 
about 25 - 30 ppm, which the fish and plant reactions say it should be. 
  Any comments?

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