The kalk reactor was added mostly to help counteract the tendency of a calcium reactor to depress the pH of the tank. This is the MyReefCreations medium-sized reactor. I added the shutoff valves on the lid to make removing the lid less messy. The reactor is fed by the Tunze Osmolator, so all topoff water is infused with kalkwasser. The stirrer runs for 10 minutes every 2 hours.