XM Lighting Double Ended HQI Lamp 250 Watt 20,000 Kelvin - The XM double-ended 20000 Kelvin metal halide bulb offers excellent coloration and good intensity. It is white with a strong blue tint. It brings out the fluorescent pigments in corals elegantly. Fluorescent supplementation is usually not necessary, but can be used for added intensity and to simulate dawn and dusk. This bulb will work with standard magnetic ballast, magnetic pulse-start ballast, magnetic HQI ballast or electronic IceCap ballasts. It must also be housed inside a pendant/uv-proof glass lens cover. It cannot be used with simply a reflector in an open application as UV rays emitted by the bulb must first be filtered with a UV-proof lens. An excellent choice for reef tanks 22 inches to 30 inches in depth. read more...