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IUnknown said:
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
You should use the initial pH reading because that is what you really interested in. The CO2 level that is in the water at the point of time.

IME, PO4 levels can vary widely without causing problems to a system where CO2, K and NO3 are well maintained. The levels in my tank varies from 0.5ppm to 30ppm at different stages (including a period where I made a boo-boo in dosing PO4) without causing problems.

BC
 

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Laith said:
30ppm PO4? wow! what were your other parameters?

No negative symptoms?
For about 1+ month I had 20-30ppm of PO4. During that period, my NO3 level was around 10-20ppm. I have kept my CO2 very high at 30-35ppm. I also dose quite a big amount of K. During that time, there was no algae problem.

If you wanted to know why I had so high PO4... I was over-enthusiastic in pluging in those NPK tabs which contain very high level of soluble PO4 in my substrate. :wink: It took me more than one month of weekly water change before I see the PO4 level easing off.

BC
 
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