PH/KH Chart - The Planted Tank Forum
Old 05-31-2014, 05:21 PM Thread Starter
Algae Grower

Join Date: Apr 2014
Location: Overland Park, KS
Posts: 68
PH/KH Chart

I guess I don't understand the PH/KH chart. I am using Tetra EasyStrips to measure my PH and KH. My problem is with the KH reading, my KH measures 120 with these strips. The KH portion of the chart runs from .5 to 15. What am I not understanding? Should I be dividing my readings by 10?
Phil G is offline

Old 05-31-2014, 05:30 PM
Planted Member

Join Date: Feb 2014
Location: Missouri
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Your measurement of 120 is probably in ppm. The chart is in degrees. Multiply by 0.056 to get degrees. Your KH for the chart would be 6.72.
aclaar877 is offline
Old 05-31-2014, 09:12 PM Thread Starter
Algae Grower

Join Date: Apr 2014
Location: Overland Park, KS
Posts: 68
Thanks, that makes the readings make sense. However, I read on this forum that the KH/PH calculation for CO2 is invalid if you have any kind of buffering in the water. I would think that most substrates and/or rocks or driftwood would tend to buffer the water to some degree, making the calculation ineffective. Is that the case, or is it not enough to be significant.
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Old 05-31-2014, 10:10 PM
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Quote:
Originally Posted by Phil G View Post
Thanks, that makes the readings make sense. However, I read on this forum that the KH/PH calculation for CO2 is invalid if you have any kind of buffering in the water. I would think that most substrates and/or rocks or driftwood would tend to buffer the water to some degree, making the calculation ineffective. Is that the case, or is it not enough to be significant.
It is definitely significant. When I first started with CO2 I tried to use that chart, but I was getting 60-70 ppm per the chart, at a low bubble rate for the CO2, and no effect from the CO2. It was only after I realized how a drop checker works, and used it, that I was able to increase the bubble rate enough to give me a significant amount of CO2 in the water. When you think you have 70 ppm of CO2, and have heard that 30-40 ppm is the optimum amount, you are very hesitant about increasing your bubble rate. It is the same as operating blind. (Experienced people can judge their CO2 by what the plants and fish are doing, but when you first start out that is very difficult to do.)

Hoppy
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Old 05-31-2014, 11:02 PM
Children Boogie

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Location: Cincinnati
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The chart works great in the laboratory with an empty tank of water, great ph sensor, and calibrated accurate kh test kit.

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Old 06-01-2014, 02:00 AM
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Originally Posted by mistergreen View Post
The chart works great in the laboratory with an empty tank of water, great ph sensor, and calibrated accurate kh test kit.

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That's true, because the chart is based on the known relationship between pH and KH of the water containing carbonate ions, plus the concentration of CO2 dissolved in the water. There is no similar chart for real world aquarium water, with other stuff in it that affect either or both pH and KH independent of each other.

Hoppy
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Old 06-02-2014, 05:38 PM Thread Starter
Algae Grower

Join Date: Apr 2014
Location: Overland Park, KS
Posts: 68
Thanks to all for the clarification. I still want to use pressurized CO2, but will probably try it in the plant grow out tank until I feel confident that I can control it to where it is not dangerous to the fish. I have had some of these fish for a very long time and would feel really bad if I killed any of them.
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