[Newt]

There is a chart based on pH and KH that will give you CO2 concentrations. I'm not at home and dont have access to it but if I remember I will attach it tonite.

 

[Newt]

Here is a link to the chart I use. It has been adjusted for the inaccuracies others have pointed out unless you have abnormally high phosphate levels and/or other buffers in which case it wont work. The same inaccuracy existes for CO2 test kits i.e. they can be thrown off by buffers. Also, a drop checker can only tell you if you are Low, OK or High - not where you are within each range which can vary considerablely.

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

........sounds a bit like someone has some kinda beef or got out of the wrong side of bed today..........