Alkalinity drop with no apparent effect on corals

[Koty]

My alkalinity was 6.3 dKh this morning. Although my tank showed no stress, the decrease may have been slow enough.
The reason was a power outbreak, after which my Reef factory x3 doser stopped dosing. My last nitrate came 0, and my phosphate was 0.1 ppm. I recently started dosing 6 x 1.5 ml/day carbon source (Elimi NP) instead of one morning shot of 1 x 4 ml. Also, since the nitrate was 0, I started dosing the TM amino acids.

 

[Randy Holmes-Farley]

The actual ocean alkalinity at 35 ppt salinity is only around 6.3 dKH, so the fact that corals can thrive there is not unreasonable.