46bfinGA, I run both , I used just a kalk reactor for a year, but then my tank couldnt keep calcium levels above 360 by itself, so I added a calcium , now my calcium is always around 450 . It just depends on how much demand you have for calcium in your tank .
The kalk reactor stirrs the kalk from the bottom a couple times a day to keep the mixture saturated, it settles out quickly and the white cloud in the reator doesnt make it to the very top of the reator which is where the topoff water is pulled from.
If you can maintian your calcium levels with just a kalk reactor thats a good way to go, calcium reactorsa give you higher levels of calcium but they really lower your ph, that is why I need to run both now, if I just run the calcium reactor without the kalk reactor my PH drops.