At AquaCave, we offer some of the best selection & best prices on Calcium Reactors and accessories for you marine and reef aquarium. Calcium reactor dose a 24 hour stream of calcium ions and carbonate ions into your reef system. This is the ideal ion pairing that the popular two-part liquid additives offer, though at a much higher long-term cost, and it is up to you to dose it daily and dose it correctly. Kalkwasser reactor is a simple and reliable way to add kalkwasser to your aquarium. Kalkwasser is an excellent source of calcium, hydroxide ions to buffer alkalinity, an unmatched ability to encourage coralline algae growth, and it precipitates phosphates out of your system water.