Kalk is reasonably safe if you at least measure PH. It will up your KH, Ca and PH. The key point to dose Kalk is that it need to be very slow, ideally use a dripper to dose Kalk, my drip rate is 1 drop/sec. I dose Kalk to maintain my PH to be above 8.0, KH will stays somewhere 7-8 for me. Ca is high for me because I also dose Coraline additive. Sent from my iPhone using Tapatalk