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Discussion Starter · #1 ·
I am using The Lamotte 4491 Alkalinity test kit to measure KH in my aquarium. I am using the results to measure the Co2 in the system using the following calculator and a pH probe,
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm
My problem is that I initially get a reading, and then the color changes as I let the sample sit (as if the Co2 is being gassed off, and my result changes). What I want to know is if I should use the initial reading to determine my Co2, or should I let the sample sit for an hour to measure my Co2?
Also, Chuck's webpage describes PO4 concentrations as a problem. I was wondering at what levels do they become a problem. I maintain 2ppm throughout the week.
Thanks,
Greg
 

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Discussion Starter · #5 ·
Hi Greg,

Thank you for using LaMotte analytical products. When performing the alkalinity (DKH) test, be sure to take the reading as soon as the sample changes from blue-green to a purple color. This will provide your true DKH reading which you can use with the CO2 calculator. Your observations are correct, the color will change as the sample sits and is exposed to ambient air (due to changes in pH). This reversion of color in the sample is typical of many titration tests, but should be ignored.

Regards,

Technical Service
LaMotte Company
 
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