Kalkwasser is German for 'Lime water'. Kalkwasser is used as a calcium supplement in marine aquariums. Marine organisms draw calcium from the water to form their skeletons and shells. Hence, the calcium level in the water gets depleted. This has to be replenished.
Kalkwasser is a solution of calcium hydroxide in water at a high pH usually above 12.
Hence, care should be taken in handling and preparing it.
Kalkwasser should be properly dosed.
Kalkwasser reacts with carbondioxide in the atmosphere and becomes calcium carbonate which is insoluble. Hence, it cannot be stored for long and should prepared before it is added.