MORE CALCIUM REACTOR INFO:

A calcium reactor is simply a container filled with calcium carbonate (CaCO 3 ) media over which aquarium water is passed with the addition of carbon dioxide. Adding carbon dioxide lowers the pH of the water, making it acidic, and dissolving the calcium carbonate to provide the aquarium with calcium and alkalinity. Calcium reactor offers a simple and convenient solution for maintaining calcium and alkalinity in your reef tank. After the initial setup, the calcium reactor requires minimal maintenance. A calcium reactor is almost a necessity for tanks heavily stocked with stony coral where calcium and alkalinity demands are high.
It is also a great addition for those looking to boost the growth of coralline algae on their live rock. Calcium reactors provide a steady supply of calcium by using CO2 to dissolve media in the reactor and, thus, releasing calcium into your water. The effluent released also acts as a buffer to stabilize pH.