I dose kalk 24/7. I add it to my 5 gallon top off resevoir. It tops off using a float switch and a aqua medic dosing pump. The only time it mixes is when I add more water to the jug. So far its going great keeping my calcium around 460 and my alk is around 7. Every now and again, I have to add reef buffer to the tank if the alk drops, My PH during the day holds around 8.1 and at night its around 7.9. I have read though that even seawater's PH drops at night in places so I wasn't sweating the minor drop in PH. I have heard of other peoples tanks hitting around 8.4 at day and dropping to 7.6 now that I would be very concerned about.
I know you want to keep it constant, but so far I haven't seen any issues.