The KW Reactor is designed with the upflow principle to achieve the most efficient use of Kalkwasser. By pushing top-off water upward through the calcium hydroxide, it automatically mixes it to achieve a supersaturated kalkwasser solution. Very convenient design that can be mounted hanging on the back of the aquarium or below the aquarium. Includes check valve and flexible connection fittings that rotate 180 degrees to allow a perfect custom fit to your installation. Threaded lid design makes adding calcium hydroxide or servicing quick and easy. Model 300 for aquariums up to 300 gallons. Patented design by Julian Sprung.