When we replaced our windows, my pH really plummeted. I tried everything I could think of or read about below.
I did the outside aeration test and that raised the pH in the glass of tank water. Like you, I now pump outside air to my skimmer, but no scrubber. raised my pH a good bit.
Crack a few windows when I can - another bump in pH.
I started dosing lots of kalkwasser, again, another good bump in pH
Put the refugium and small frag tank on opposite photoperiods - another bump in pH.
Added a larger frag tank on opposite photoperiods - another bump in pH.
I also calibrate my probes quarterly or more and replace them once a year. I use BRS double junction. Calibrating usually make pH drop suggesting my probes drift upwards over time.
The largest pH boost comes when I can open all the windows for a few days (suggesting high indoor CO2) and also when I added the large frag tank and filled it with corals.
I don't think any one solution will fix your issue, but a number of small fixes will. Most of the above fixes bumped pH by only 0.1 or usually less, but the effect is additive and my previous pH range of 7.7-7.9 is now usually 8.1-8.3.
I did the outside aeration test and that raised the pH in the glass of tank water. Like you, I now pump outside air to my skimmer, but no scrubber. raised my pH a good bit.
Crack a few windows when I can - another bump in pH.
I started dosing lots of kalkwasser, again, another good bump in pH
Put the refugium and small frag tank on opposite photoperiods - another bump in pH.
Added a larger frag tank on opposite photoperiods - another bump in pH.
I also calibrate my probes quarterly or more and replace them once a year. I use BRS double junction. Calibrating usually make pH drop suggesting my probes drift upwards over time.
The largest pH boost comes when I can open all the windows for a few days (suggesting high indoor CO2) and also when I added the large frag tank and filled it with corals.
I don't think any one solution will fix your issue, but a number of small fixes will. Most of the above fixes bumped pH by only 0.1 or usually less, but the effect is additive and my previous pH range of 7.7-7.9 is now usually 8.1-8.3.