My 1500g system when loaded and dialed in drops .5dkh per hour when he sun is up (2 outdoor 180g frag tanks). I run a giant Dastaco CaRc and Topoff is thru a custom Avast Kalk Stirrer.
During the summer months we may evaporate out upto 70g a day of water using evaporative cooling and we replace all that with Kalk.
FWIW, I prefer limewater (kalkwasser) dosing from a settled reservoir as opposed to a stirrer because it is easier to control potency, settle out impurities, and add vinegar if you want to boost the potency.