The German-made Radium 20000K metal halide bulb offers excellent coloration and good intensity. It is crisp-white with a strong blue tint. It brings out the fluorescent pigments in corals nicely. Fluorescent supplementation is usually not necessary, but can be used for added intensity and to simulate dawn and dusk. An electronic ballast, magnetic pulse-start ballast or magnetic HQI ballast is required to ignite this bulb. This bulb is white with a blue tint on a
magnetic HQI ballast. It will burn more blue on an electronic ballast or pulse-start ballast. An excellent choice for  reef tanks 22"–30" deep.