What is ‘stable’ pH?

[ClownSchool]

Five months ago, I had a 55 gallon mixed reef tank with a canister filter and my pH was tested using a Hanna meter.
I read it was best to test in the evenings, at the end of the photo cycle, and my tests consistently read just above 8.2.
BUT….since I moved everything over to a RedSea 350 with a sump, 90~ gallon total volume, and an Apex pH probe, I’ve had a problem keeping it above 8.0, and my lows are surprisingly low.
I use EVS two-part with the DOS and add 2ml of Kalkwasser in R/O every morning.

Does anyone have any advice on raising pH?
And,
What should a healthy tank’s pH swing be over 24 hours?
(The most recent dip in pH may have been due to using Aiptasia F)

 

[Stephen Glover]

I dose kalk from 12am to 11am. then 2 part during the day. I only run my skimmer (with a c02 scrubber) when the ph falls bellow 8.3. The pH also reacts to whether I’m able to open the windows or not. My pH is between 8.25 and 8.4. I think it’s making a huge difference but have only been running it this way for a month or so.