The point I was making is chasing pH via kalk dosing is not a wise idea. Ph fluctuates due to multiple environmental issues. Weather, barometric pressure, amount of people, animals in the room ect ect. To many people are now misusing kalk due to the pH buffering effect. Now people are chasing pH like they used to phosphate and nitrates.
How much consumption of dkh do you have? I doubt it's enough that your not able to just shut down the 2 part dosing while dosing kalk at night. Additionally are you dosing 2 part or 3 part?
if your dosing So much kalk at night that your having an increase in dkh lower the kalk dosage or shut down the 2 part and increase kalk to maintain the dkh throughout the nite. Simple solutions.
I'm doing the BRS hyrbid balling method. So Alk, Ca, and Balling Salt.
The tank is loaded with SPS and there is consumption at night. I used to let the Trident control the dosing and opted for the "dose less at night" option, but I never thought to look at what ratios they're using at night. That seemed to work reasonably well and keep the numbers consistent between day and night.
I should probably mention, as far as chasing pH... This is not my only pH control tactic. I am also using a C02 scrubber that is managed by the Apex' pH probe and controls an electronic ball valve to switch to ambient air the pH gets too high. The skimmer associated with the scrubber is also tied to the doser that doses Kalk at night. Same thing, pH gets way way too high, it shuts down both the skimmer and the Kalk doser. That's never happened to date though (knock on wood).
I also have an ERV unit. It's undersized, but AC company should be fixing that in the next week or two. So my C02 values are probably a lot lower than most. On the weekends, when my office is closed, it's actually really close to outside air (I have a C02 monitor near the tank). During the week, the undersized ERV helps, but I'm not keeping consistent C02 levels, hence the need to put a bigger CFM ERV in.
So for me, it's not unrealistic to peg my pH between 8.3 and 8.45. I'm actually pretty close to that right now. The last piece is finding a way to keep the pH above 8.3 at the bottom of the diurnal cycle, using both two part and Kalk (I don't think Kalk will cover all the demand), at least in the volume I'm dosing and the concentration I'm using), but not overshoot my Alk target.