# CO2 and 0 kH



## stevenlau (Jul 21, 2009)

Is it true that it is hard to measure dissolve CO2 in water of 0 dkH using Drop Checker? Why? 

Thank you.


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## bsmith (Dec 13, 2006)

Are you talking about the water in the tank or the water mixed with ph reagent in the Drop Checker?


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## stevenlau (Jul 21, 2009)

Ooops...The water in the tank. Sorry for my bad english  Thank you.


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## stevenlau (Jul 21, 2009)

Bumps...


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## Diana K (Dec 20, 2007)

Not sure if this answers the question...

In a drop checker you will have a specific amount of carbonates, to make the water read 4 German degrees of hardness. As the air above the tank water (inside the drop checker) has CO2 in a ratio with the tank water, this CO2 will enter the test solution in that ratio and change the pH reagent to give you a reading. Testing the drop checker for pH involves simply KH and CO2. Nothing else to affect the pH. 

Testing tank water for KH and pH includes all the other things in the tank water that can affect the pH, such as phosphates, organic matter, tannic acids and other things. You do not know what or how much of each affects the pH, so you do not know how much the CO2 is affecting the pH unless you do a comparison test. 

1) Test tank water for pH before turning on the CO2. 
Make no changes to anything else, just turn on CO2. 
2) Test the tank water for pH while the CO2 is running, after it has had a chance to circulate and be well mixed with the water. 

The difference is caused by the CO2 (since you were very careful not to make any other changes in the set up) so you can use that drop in the pH to determine how much CO2 is in the water.


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## stevenlau (Jul 21, 2009)

My tank water is 6.8 pH, decrease further by ADA AS II to 6.2 before CO2 is on and 5.2 after CO2 is off at night. The Drop Checker is lime green at the last 2 hours before CO2 is off and turn to blue at the morning before CO2 is on.

Just read somewhere that stated having 0 dkH will be impossible to determine the dissolved CO2.

Thank you Diana.


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## Diana K (Dec 20, 2007)

I think those colors in the drop checker are correct. Some shade of green indicates about the right level of CO2, and the blue shows very little CO2 in the water.


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## stevenlau (Jul 21, 2009)

Glad to know it from you. Thanks


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## mikaila31 (Feb 24, 2006)

0 kH means your water has very little buffering ability and the pH will change a lot as you are seeing. You might want to add something to bring that up. Using a calcium fertilizer will do that. For example my hard water, pH 7.6, kH 8, does not like to fluctuate CO2 being on only changes pH by .4-.6 at 30ppm.


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## DVS (Nov 20, 2005)

mikaila31 said:


> 0 kH means your water has very little buffering ability and the pH will change a lot as you are seeing. You might want to add something to bring that up. Using a calcium fertilizer will do that. For example my hard water, pH 7.6, kH 8, does not like to fluctuate CO2 being on only changes pH by .4-.6 at 30ppm.


If your pH only changes by .4 to .6, you only have approximately 15 ppm of CO2. The relationship is constant. Calcium chloride and calcium sulfate will have no effect on ph or kH. Calcium carbonate will.


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## ashappard (Jun 3, 2006)

over the years, I think many in the hobby have realized that pH fluctuation due to CO2 injection is not harmful to livestock. Too much CO2, that can be harmful. TDS fluctuation, that can be harmful.

if your tank is clean, and the dosing is good - dont fret pH. I dont measure it anymore, going on a few years now.


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