Kalk $ calcium reactors?

[Doug]

A kalk reactor mixes kalk with fresh water to be pumped slowly into the sump/tank, to replace evaporated water.

A calcium reactor or co2 reactor, uses a cylinder full of aragonite media. Saltwater is fed slowly to it and circulated through the media with a small pump. The ph of the water contained inside the cylinder is lower by the injection of co2 into the chamber. The lower ph allows the dissolution of the media, which, {depending on the media} adds calcium, strontium, magnesium and alkalinity to the aquarium.