Originally posted by SNPiccolo5
However, the pH may remain at 8.5, which is of little importance since the KH does go down.
My main concern is getting the KH low enough so when I add CO2 the pH drops below 7.
If that's your concern, an easy way to ease your mind would be to simply mix up a very small test batch of 50/50 water in a jar... let it sit for an hour or so (to let the ion balance that regulates pH re-establish)... and test the parameters (GH/KH/pH) of your test sample. Then you'll know, very closely, what you're going to get before you go "all the way" and change your tank water.
You may find that the GH/KH in your tank ends up a little bit higher than in the test sample after a day or so IF there are items in your tank/filter that have collected "mineral" deposits. With the lower GH/KH, deposits on things (if there are any) could partially dissolve back into the water. However, after a few water changes, this process should stop.
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