Hey R2R, I been noticing my pH in my 300 reef started trending up slowly recently. Back in mid September, my pH would bottom out at 8 at night and peak to 8.2 throughout the day. Slowly since, the peak has started to climb, and is now reaching 8.38 and bottoming out at 8.23. The tank is fairly new, and I started adding corals in it since beginning of September. I run a calcium reactor and kalk reactor to replenish alk and calcium. I'm currently not dosing anything else at the moment. I do use a hose that takes fresh air from the outside to inject it into the skimmer. Parameters have remained stable throughout, alk 8.5 calcium 450 mag 1500. I don't see any adverse effects in the corals and they seem to be growing okay. Any ideas to why pH is climbing slowly?