I never could get my ato top off to work well with the controller. Similar to a voltage surge at the end of a long 100 amp cable... generator runs at 24%, you turn on a large power consumer, draws heavily on the generator, the generator spins up, power surge. With the dosing, I would have my machine kick on the kalk at 7.8... it would run for about an hour before my sensor would register the climb in PH... and half an hour later I would have an alarm for an hour as my PH would be too high. What always worked for me was the evaporative top off, although I toyed with a steady drip drop, drippity drop drop. I thought you didn't have any sps? If you don't have a requirement for the extra calcium, why bother? Or are you chasing PH?