I watched the PH both when I added the Kalkwasser last night and this morning....the highest point was around 8.3 around midnight (about an hour and a half after adding it) and then this morning it was back down to around 7.8 (for some reason my PH is not staying up in the 8s despite my best effort)....I'm checking it with a calibrated (just yesterday) digital PH probe on my Reef Pro 2