Hi all,
Perfect, the dGH is the <"German"> value, so dKH = 3.45. One dKH is equivalent to <"21.8 ppm bicarbonate (HCO3-)">.
We have a map <"Some handy facts about water">, but tap water can be very variable over short distances,
They use both, the shell is the "aragonite" form of CaCO3. Have...