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crisps

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How do you calculate the CO2 level in your tank from the pH and was it either GH or KH?

I tried searching but ph and kh are to short to search for.

Thanks,

Rex Grigg

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You take a pH and kH reading and use a chart like you can find in my Guide.

crisps

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According to my test kit (5 in 1 quick dip) Alkalinity (KH) is roughly 100ppm and pH is roughly 7.0.

Any idea how to convert KH to the same units you are using? Is it logarithmic or something as your scale i between 0 and 20.

Buckeye_Robert

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How is hardness measured? There are two units commonly used in measuring hardness: German Degrees of Hardness (dH) and Parts Per Million (ppm). One dH = 17 ppm. For a rule of thumb:

0 to 4 dH 0 to 70 ppm very soft
4 to 8 dH 70 to 125 ppm soft
8 to 12 dH 125 to 200 ppm medium hard
12 to 18 dH 200 to 300 ppm hard
18 to 30 dH 300 to 500 ppm very hard
over 30 dH over 500 ppm extremely hard

crisps

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Thanks, I make it very roughly 18ppm CO2.

I have no Co2 injection at all so that seems quite good.

Rex Grigg

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If you have no CO2 injection then you have no CO2. Something else is affecting the pH. You actually have at best 2-3 ppm. TANSTAAFL* applies here.

The pH/kH/CO2 chart is based on the only buffers in the system being bicarbonates and CO2. If you have peat or wood in the tank these can lower the pH. If you are using some witches brew to lower the pH to try and get some "ideal" pH then that affects the chart.

*There Ain't No Such Thing As A Free Lunch. Comes from the Dean of Science Fiction.

Hoppy

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If you want to know how much CO2 is in your water you can't do "roughly" measurements of pH, especially, and KH. You need to know the pH within +/-0.1 and the KH within +/-0.5dKH. That means either good titration test kits or a pH meter and a good KH test kit.

Unfortunately, you still won't know how much CO2 is in the water unless you use a drop checker with known KH distilled or DI water in the bulb. Aquarium water typically doesn't meet the criteria of having only CO2 and carbonates affecting its pH and KH.

caymandiver75

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If you want to know how much CO2 is in your water you can't do "roughly" measurements of pH, especially, and KH. You need to know the pH within +/-0.1 and the KH within +/-0.5dKH. That means either good titration test kits or a pH meter and a good KH test kit.

Unfortunately, you still won't know how much CO2 is in the water unless you use a drop checker with known KH distilled or DI water in the bulb. Aquarium water typically doesn't meet the criteria of having only CO2 and carbonates affecting its pH and KH.
I'm using a drop checker with 5 KH of distilled water in the cheapo red sea unit and man it's hard to distinguish the shade of green. It could be 6.7 or 6.4 and I wouldn't really be able to tell. I guess that is why I'm using 5 KH, as long as it's of some shade of green with no blue tint I should be above 30ppm CO2.

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