I have an established 75g tank(7 years with fish) that I recently planted about a month ago. The plants are doing quite well(a lot of new growth) and I have a pressurized CO2 setup ready to go(currently dosing Excel). I am puzzled by my water tests though especially the KH. KH is 1, GH is 240, and PH is 6.8. PH has been very consistent and I'm seeing no swings, but despite adding baking soda my KH will not rise. It will rise temporarily to 2 but then come back down within 24-48 hours. I am dosing per the online calculators. In my 180 cichlid tank it is testing a KH of 4, GH 240 and from the tap my water is KH of 4 and GH of 240.
I would be pleased if I could maintain the KH o4 from the tap. What if anything do I need to do? Since PH is steady do I not worry about the KH and go ahead with the CO2?