Without any macro algae in refugium, then my theory falls apart. There must be something else in your house affecting the CO2 levels in your basement and subsequently, your tank's pH.
Back to the gas water heater in your basement, shouldn't something burning consume oxygen? Could that be affecting the CO2 levels in your basement?
Back to the gas water heater in your basement, shouldn't something burning consume oxygen? Could that be affecting the CO2 levels in your basement?