apex dosing

Hi there, I'm currently having some clogging problems with one of my feed vessels (I'm experimenting using different feed stocks) so I'm trying to feed my tank every minute 24/7. I have been able to program my APEX pump to feed every minute using the Feed system, however I can't appear to find...

So I'm using a classic Apex system with an EB 8 and a BRS doser 1.1 ml. I slowly add kalk throughout the day and it's at a constant rate every hour. At night the tank will drop in PH even though I'm dosing kalk. So far Ive got my PH up to 8.2 and it will drop down to about 7.98 when the lights...