How much kalk powder to add to kalk stirrer?

[14 foot reef]

What Brand stirrer do you have?

 

[chimbo84]

I use the same unit Avast K2 - I'm still using the PH probe not the conductivity probe though. I found the Avast can handle a pretty large overfilling before having any issues of bogging motor down or stopping completely. I have been using the unit for about a year now and I have 2 K1's on systems I manage. what I found is if your PH is 12.3
( the target you want to see ) then as soon as it drops to 12.2 / 12.1 immediately add a cup of dry kalk powder to the stirrer. If you wait longer than a day it will drop really quickly to the 11's and that is basically not very effective, if at all.
Soon as you add the 1 cup it will jump back to 12.3 and stay there until the next drop to 12.2 / 12.1. I found I'm adding about 1 cup per month on 850 gallons, with my PH & Alk staying unbelievably stable. I kinda follow the Chris Meckly reverse lighting process of dosing the 24 hour evaporation in a 14 hour lights off period. My PH stays 8.3-8.35 day and night and my alk stays 8.5 - 8.6 consistently.

How frequently do you calibrate the pH probe in your stirrer? I just added a probe and it’s reading 13 before calibration. Just curious how often I should expect to calibrate the probe for this extreme environment.

 

[14 foot reef]

How frequently do you calibrate the pH probe in your stirrer? I just added a probe and it’s reading 13 before calibration. Just curious how often I should expect to calibrate the probe for this extreme environment.

The PH probe is not going to be Super accurate in these conditions. I basically use mine to see any drop at all from its number it reads. Mine reads 12.5 If it drop to 12.3 or 12.2 I know I need to add Kalk Powder. I would treat your the same way, as soon as it moves off 13, add Kalk Powder.