I disagree on it being a plumbing issue ;)

My pellet reactor output goes right into skimmer input. My pH is on the low side. Always. It doesn't swing much. I believe I have more CO2 production from the pellets than other people because I feed more. Easy as that. You feed your cows more hay they poop more. No magic there.

Better aeration helps a lot. My new spray skimmer can balance it much more than the needlewheel could.