The PhosBan Reactor 550 is designed with the upflow principle to achieve the most efficient use of PhosBan® or other chemical filter media. By pushing water from the bottom upward through a dispersion plate, it forces an even distribution of water through the media, and prevents channeling. It can be mounted hanging on the back of the aquarium or below the aquarium. Includes ball valve for regulating flow, and flexible connection fittings that rotate 180 degrees to allow a perfect custom fit to your installation. The threaded lid design makes servicing quick and easy. One reactor for aquariums up to 600 gallons.