Sorry to sorta thread jack but Im curious, does KH matter at all in a tank with active soil? Or because the soil buffers you dont need KH and the soil keeps the PH from swinging?
Yea that's completely correct. kH helps buffer the pH and keep it stable, but if you have active substrate it is doing the buffering so keeping the kH around zero you minimize the "work" the substrate has to put in to lower the pH.
The numbers you quoted are from the water out of the RO/DI filter. My tap water is:
KH 5 (drops to color change, API test kit)
GH 6 (drops to color change, API test kit)
Yea I meant are you sure the kH and gH values from your RO/DI filter are correct? Or is your TDS measurement in degrees? Generally, if you're using a TDS meter it will measure in ppm, whereas the kH and gH tests are in degrees. In which case your TDS should at least be ~38.