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Hello,
First off I am very new to this hobby... apologies if this is an obvious question but I am struggling to understand how to get the proper water chemistry for optimum CO2 absorption. Out of the tap my water is very soft with a dKH of about 2 and a PH of 7.2 and very low chlorine. From my understanding, at such low KH levels for a PH of 7.2 the level of CO2 absorption is very low. However I seem stuck as attempts to raise KH with an alkalinity buffer, it raises the PH, no surprise there . Raising the dKH to about 5-6 also raises the PH to about 8.0 and adding enough PH Down to get the level to 7.2 results in the dKH back at 2. The laws of science hold true in this house!

So I am really curious how I can affect one value without the other, how can I better optimize my chemistry?

One idea I have (and I am looking for a sanity check for this) is to raise the KH back to say 6-8 knowing the tank is going to go slightly alkaline and then pump my CO2 up to some thing like 10 bubbles per second to bring the PH down as a result of the carbonic acid induced into the tank. However, wouldn't that just drop the KH like the PH down did? Or does carbonic acid react differently to dissolved carbonates in the water column? Any education about this is greatly appreciated!
 

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Do yourself a favor and don't mess with Kh :)

2 dKh is a beautiful thing for plants and I do think you have that backwards. Lower kh is generally perceived as being easier for co2 absorption. Not that I necessarily agree with that.

If you read through old posts over on the Barr report that discuss this issue you will see a few (I'm thinking of the ones that Tom Barr himself is apart of) that say in theory there is a difference but in reality not so much.

My .02 cents :)



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