kalkwasser

[xenon]

Kalk is an excellent way to maintain calcium and alkalinity in a balanced way. The major advantage is that it also increases PH.

Wit that said, there is only so much kalk you can dose when you saturate your top-off water with kalk. If you have a heavily stocked tank (lots of corals) it won't be enough.

You can alternatively blow a fan across the water surface of your tank to evaporate more water so that you can top-off even more but it may still not be enough evaporation to keep up with demand.

I know what some with heavily stocked tanks top-off with kalk and also use a dosing pump. The reason for this is the increase in PH from kalk.