My tank / tap measures +7dGH. Should I dose APT SKY?Updated a month ago
No.
GH measures the total amount of Ca/Mg ions in the water (and other divalent cations).
It is likely that your tap water has significant amounts of Calcium or Magnesium or both. In the event that your GH is made up entirely of Calcium, you should dose a pure magnesium salt, instead of APT SKY.