Types of water hardness
There are three types of water hardnss, that are important for aquarium:
Temporary (carbonate) hardness (dKH). It's the hardness derived mainly from carbonate and bicarbonate ions AKA alkalinity hardness. Can be reduced by boiling: Ca(HCO3)2 ― t→ CaCO3↓ + CO2 + H2O Mg(HCO3)2 ― t→ MgCO3↓ + CO2 + H2O
Permanent hardness (dNKH) Can NOT be reduced by boiling. This if concentration of sulphates, nitrates, chlorides etc. For example CaCl2, MgSO4 etc.
General hardness (dGH) General hardness is a sum of two prior ones: dGH = dKH + dNKH
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