My PH level runs at 7.8-7.9 w Cal reactor and dripping Kalk at night. I gave up worrying about it and let it sit there - no ill effects are observable after months in that range.

One thing that helped a little was running my effluent into my skimmer - seems to blow off more CO2 before it hits the main tank.

You may also want to make sure you are refreshing the air in your room - my ph goes up abit if the house is empty, and drops abit with more bodies. Opening a window near the tank helps stabilize those swings...