Been having some issues with my pH on a 70g system. The pH was struggling to go above 7.9 and I decided to add a co2 scrubber reactor to the skimmer. This got the pH to 8.1 but would keep dropping down to 7.9 at night which is expected especially sonce I don't have a refugium. I was having fits with my skimmer so I got a new skimmer and with the co2 scrubber and new skimmer pH was fluctuating from 8.16 at night to 8.2 just before lights off. After getting home from the holidays and ph holding steady I had to do two water changes due to some plumbing issues resulting in two roughly 20% water changes in 36 hours. The pH is now struggling to go above 7.9 according to my apex I tested with red sea ph test kit amd got pH of 8.0 and recalibrated my pH probe. Dkh is 7.7 accordong to my hanna tester with new reagent. I only have two lps corals and some zoas so I don't done and don't put kalk in the ato Reservoir. Should I start adding some kalk to it or should I just accept that stable 7.9 and not worry about chasing a 8.2pH? I do not have a calcium or magnesium test kit due to the low number of corals and only 2 lps corals. All corals look good and the lps are growing. Thoughts? Could the co2 media be used up even though it is almost all white still and not purple to indicate it has been exhausted? The wi dows were also open for about 12 hours. Running the skimmer airline outside is not an option.