Kalk Stirrers: The addition of Kalkwasser ( Calcium hydroxide) today is now widely accepted as a means to keep Calcium levels high. Kalkwasser is simply Calcium Hydroxide dissolved in water, the use of Kalkwasser is well documented and very well proven in the keeping of hard corals and its use is recommended. Kalkwasser when mixed with RO water is alkaline with a pH of 12.6! You cannot simply mix Kalkwasser and just drop buckets loads into your system. This would cause a massive pH rise and the death of your fish and inverts. It must be added gradually ideally to replace evaporated water from you reef. 
The best method that is now currently available is the use of Kalk mixers/stirrers.