Originally Posted by Hoppy
If you read carefully, Chuck Gadd notes in his discussion that the equation is not valid for water that isn't "perfect".
Is it possible to have an planted tank pH 7 @ 6dKH without supplemental CO2 or non carbonate buffers (e.g. phosphates)? According to the chart CO2 would be ~18ppm, well above normal equilibrium values of 0-5ppm