I've had some fish deaths lately and paying attention to water params, I've gotten a little concerned about my pH levels. My tap water comes out of the tap with a pH of around 7.6. After aging it overnight it ends up being around 8.0.
However, a week after a water change my aquarium tends to be around 6.8 - 7.0. If I then do, say, a 50 % water change it puts my pH up to around 7.2 immediately and then around 7.8 the next day as it ages, which can give me a swing of up to 1. This seems like a lot for the fish! And then from 7.8 a week later I'm back down to 6.8 - 7.0.
The tank is planted and CO2 injected but the CO2 is on very low. My KH and GH out of the tap are both around 5 drops, but after a week in the tank this also drops (down to 2 - 3 drops).
I'm trying to figure out a water change schedule or something else I can do to keep things more stable and I'm starting to wonder if the only solution is to do water changes every 2-3 days, which seems like a real hassle!