Kalkwasser Reactor. The Kalkwasser Reastor is a sealed unit designed to supply reef aquaria with calcium by enriching the fresh water top up supply. It uses the Kalkwasser-method and is filled with calcium hydroxide, which is agitated by a pump. It is possible to automate the system by combining an automatic level controller such as the ab aquaniveau single with the Aqua Medic Kalkwasser Reactor. The reactor is engineered to take a pH electrode to control the quality of the kalkwasser. An additional advantage of this method is, that phosphate is removed from the top up and the aquarium water.