I just tested the output of my Osmio zero. Filters are 11 months old. KH is 26.9 and GH was negligible (seemed to turn green after first drop and remained green thereafter with more drops added). This confuses me as I thought KH is carbonate hardness (hardness due to bicarbonates alone) whereas GH is general hardness (hardness contributed by all contributers), hence I would have imagined GH would be greater than KH? Any thoughts on this? I use the API drop test kit, 40ml sample, results divided by 4