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. Rated for aquariums up to 1250 gallons.