Kalkwasser (lime water)
Kalkwasser is a saturated solution of calcium hydroxide used to supplement calcium and KH simultaneously. An ancient but still effective method.
Detailed explanation
Kalkwasser is prepared by dissolving calcium hydroxide (slaked lime) in RO water. The resulting solution has a very high pH (12+) and contains approximately 800 ppm of calcium.
It is administered as top-up water. Every litre of evaporated water is replaced with kalkwasser. This way you supplement calcium and KH without adding extra water volume.
Advantages: simplicity, very low cost, precipitates phosphates (anti-algae effect), raises the pH.
Disadvantages: The amount of calcium you can administer is limited by evaporation. If the aquarium consumes more calcium than the kalkwasser can provide, additional supplementation is needed (balling or calcium reactor). The very high pH of the solution requires slow and diluted dosing.
The kalkwasser must be administered drop by drop in the area with the highest circulation (near the return pump) to avoid areas with pH 12 which would kill everything. Never pour it directly into the aquarium.
For aquariums with low calcium consumption (few corals, predominant soft corals) kalkwasser may be sufficient as the only supplement. For an intensive reef SPS is usually not enough and must be combined with Balling.
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