jasonkola, I am using exactly what you are suggesting.
I have a 100L holding tank. I premix my kalk water 24 hours before, let it settle, then dump in the 100L holding tank. I use 32L canola oil pails to mix the and settle the kalk water.
My sump is rather small, only 8g on a 75g tank. I use water switch that triggers on a water depth change in the sump of 1/8". I have a MaxiJet 1200 in the bottom of the holding tank with a small valve to restrict the flow of Kalk water into the sump to a trickle as not tp PH shock the sump.
The the water level in the sump drops 1/8", pump turns on a raises the water the 1/8" over a 45 second period. The local PH change (in the sump) never exceeds 8.5. The display tank stays stable at 8.1 to 8.3 depending on the time of day.
Simple and works very well for me.