I don’t know much about Kh but mine is very high. My aquarium (and tap) water takes 17-18 drops of Kh solution to turn the vial yellow using the API Gh & Kh test kit. I believe that is about 322 ppm? My water is super soft though (because of the water softener) at only 2 drops/degrees or 36 ppm and my ph is around 7.8. I have harlequin rasboras, cardinal tetras, honey gouramis, Cory catfish, and 2 snails (mystery and nerite) in my aquarium. I don’t know much about Kh but it’s very high. Should I lower it? If so, can I mix some of our filtered water with the tap? I know they don’t recommend using filtered but I’m wondering if mixing it with tap water would be okay? I did a test of about 60% tank water and 40% filtered water and the Kh was 10 drops/degrees which is about 179 ppm.