# KH same as dKH?



## pretzelb (Nov 13, 2005)

I finally picked up a KH test kit and went to my experimental 10g plant tank with diy co2 to compare the values to the pH / KH chart ( as seen here) but I became confused with the instructions on the kit. The instructions tell you count the drops you add until you get the color change and then use their chart to convert from dKH to a KH ppm measurement (multiplying by 17.something). The charts I see only say KH with values of .5 to 10 or 20. I'm not sure how to match my results to the KH/pH charts.

I also have a follow up question on pH. If I read my tap water pH value correctly, I have a pH of 8 out of the tap. I say "if" because my kit has two bottles for testing pH - a normal one and a high pH test. The normal test shows the max value (7.6 I think) so I try the high pH test and it appears to hit 8.

Assuming my water is a pH of 8, does that mean I need to take measures to lower it in order to hit a good range of co2? Looking at the charts a value for pH of 8 is never listed so I assume this mean that it's too high to measure or achieve.


----------



## hoppycalif (Apr 7, 2005)

KH test kits, if they are all like mine, give you a degree of KH for every drop of reagent it takes to get the color change. And, it it degrees KH that you use for the KH/PH chart to see how much CO2 is dissolved in the water. You can hit a good range of CO2 no matter what the KH is (within reason of course). The amount of CO2 in the water depends only on how much you get dissolved into the water - changing the KH doesn't change that. One thing you may run into, as I have, is that the KH/PH chart gives incorrect ppm for CO2, probably due to something in the water buffering the PH. So, I am leaning very strongly to just using the plants and fish as the "meter" for checking CO2 - if the fish are showing distress you have too much, otherwise you can always use some more.


----------

