I've actually just started to research this. I am not at the point of dosing kalk just yet but I feel I'd rather dose VS run through my ATO.
I dosed via ATO since I started with Kalkwasser, probably 1996 or so. Always liked Kalk, it's a very good solution for Calc/alk in a non-demanding tank. Always had a few problems with this method. Either (A) I suspend my ATO pump in Kalk, which is really hard on the pump, and for me, was always a pain to maintain, or (B) I used an inline reactor. You can't control saturation on an inline reactor very well... it's ether full strength, or nothing, so you get a way higher dose when it's hot and dry than you do when it's cool and wet.
Changed to dosing via pump with this tank, about 6 months ago. I mix up a bucket every other week, while I'm doing a water change, usually, drop the dosing tube in when it settles, and I'm good. Same dose, regardless of evaporation rate. So far, it's been rock solid.