The Aqua Medic Calcium Reactor is a module for the creation of a natural calcium carbonic acid equilibrium in the aquarium. It is filled with hydrocarbonate. As calcium carbonate is not soluble at pH values, that are recommended in seawater aquaria, CO2 has to be injected into the reactor. This results in a local decrease of the pH and the solution of Calcium hydrogen carbonate. This way of calcium dosing does not effect the pH, like the use of "Kalkwasser".

Reactors include a circulation pump and Hydro Carbonate media. A bubble counter is required but not included. Model 1000 is rated up to 180 gallons.