Calcium Reactor Question

[nteague]

Does a calcium reactor calcify water from the tank and put it back in, or does it require an outside source of water to add to the tank?

 

[robchuck]

A calcium reactor takes water from the tank and pushes it through a chamber filled with aragonite media where CO2 is also injected. The CO2 lowers the pH in the chamber, which melts the media, the water absorbs the melted media (filled with calcium and other essential elements) and the water is then is pushed back into the aquarium.
A Kalkwasser Reactor (aka Nilsen Reactor) requires an outside source of water; K-Reactors are run in-line through top-off systems.