What's causing the pH reduction in the tank?
To be honest I'm not 100% sure and would definitely appreciate any input. Here's my thought process and working theory thus far though:
Originally the pH was stabilizing at 6.6-6.8 while the tank was cycling and nitrites were spiking at 5.0 ppm+. I read that the nitrite phase of a new cycle can lower your pH so my original theory was that after nitrites dropped and I did a large water change, the pH would stay at a higher level that was closer to the tap value.
After the nitrites had remained at zero for a few days, I did a 50% water change and tested the tank water immediately after. The tank pH tested at 8.2 so very close to the tap (was glad I didn't have any fish at that point!). The next morning though I tested the pH again and it had dropped back to 6.6 in the tank overnight.
From what I've read, water utilities can artificially raise pH levels in their water to prevent acidic water from affecting old pipes. My working theory is that my pH is being raised in this way, but is eventually dropping back to a lower level more in line with the very low KH of the water. My understanding of this is admittedly very limited but if I'm following correctly, typically low KH = low pH and high KH = high pH? Definitely correct me if this is wrong, I'm still trying to get a grasp on all of this.
I was hoping that simply letting the tap water sit out overnight would be enough to drop the pH but it only went from 8.4 to 8.2. Fingers crossed that the air stone will be the missing element that I need as I would love to avoid using chemicals.
Any suggestions/feedback would be greatly appreciated!