The comment that kalk is taking a step back is accurate...but in a specific context. Kalkwasser reactors generally function off of evaporation only, so in that instance, there is a finite amount of ca and alk you can supplement through using one.
2 part dosing has the potential to carry a MUCH heavier load used alone vs Kalkwasser used alone. Kalkwasser can only dissolve so much in water before it saturates. 2 part additives are MUCH more concentrated and you can add a tremendous amount more supplementation before actually running into rising water levels.
So in that context he/she is accurate in that Kalkwasser is taking a step back. Because it cannot carry as heavy of a load on its own.
A calcium reactor is the best option for two reasons. One, it can handle an even heavier load of supplementation than both 2 part and Kalkwasser can, and without the detriment of changing your water level, or having a dependence on evaporation, since they run a closed loop circulation rather than adding fluid to the tank.
Second, calcium reactors function by dissolving actual coral skeleton and aragonite, so they also add perfect balanced amounts of ca, alk, and trace elements in the actual proportions used for skeletonogenesis. It will not cause salinity fluctuations, require frequent mixing and refilling of containers, ect. Just set it. Test alk weekly and adjust the reactor ph and effluent to keep up with demand. In those ways a calcium reactor is superior. Yes it's more expensive, and you have to check on the lines and pumps just as regularly as you would anything else, but they just are cheaper in the long run and can handle the heaviest load of all available options.
