A kalk reactor is fine if you keep up with your demand. Some benifits are; higher pH and it precipitates phosphate.
Kalk reactors work by replacing evaportated water with saturated calcium. If youre calcium demand is really high and the tank doesn't evaporat enough... you can't dose enough. It has a max, IMO. That's the way I look at it anyways. Properly mixed kalk has a pH of 12 that's why you can't add to much of it aswell.
A reactor is nice because it's almost "set and forget" and doses minerals from the media. Since reactors has a low effluent pH I use kalk to replace all evaporated water aswell so I get the best of both worlds.
