If you have corals in your tank, yes u may use kalkwasser. Kalkwasser will boost coralline algae grows also. I know people that use calcium reactor and top-off with kalkwasser. There are a lot of advantages on using kalkwasser as well as some disadvantages. One of them is it takes some time to mix, let it stand, control drip rate. I figured my weekly evaporation rate, bought cannister wich will hold all water which will evaporate within a week. So i prepare the mix ones a week, let it stand for at least 4 hours, open the main valve, adjust the drip rate. That's it. Let me know if you wanna see pix of it.