My levels are comparable to yours. I mainly dose Ca and Alk but when I need a ph "boost" I'll mix some Kalkwasser in salt water and raise it up. I notice bigger swings when my windows are closed, obviously due to carbon dioxide not being expelled. I've been watching my corals and they seem to be doing just fine though. However, there has been a day or 2 when the ph drops below 7.7 and I notice one or 2 of my corals responding negatively. If I had my way I'd would love a stable 8.2 ph but if I try to get it that high it just plummets quickly at night so I stopped chasing a number and my corals are just fine. HTH