How to Compare Metal Halide Lighting
- 1). Count the number of ends. Many metal halide lights are single ended, which has a thread similar to a normal bulb that is used around the house. Single ended are referred to as mogul based, because they screw into their socket. Single-ended bulbs are larger than double-ended bulbs and require more space to mount. Most single-ended bulbs have a wider illumination radius than double-ended units. The double-ended metal halide lights have ceramic end caps, which hold the bulbs in their sockets. Double-ended metal halide bulbs, which are also termed high quartz iodide bulbs, are available in 70 watts, 150 watts and 250 watts. The double-ended metal halide bulb, which is smaller than the single-ended bulb, requires a special ballast to function.
- 2). Choose bulbs with a second glass shield. Single-ended metal halide bulbs have a protective glass shield or envelope that encases the arc tube and filters out much of the UV rays that are emitted. Double-ended lights have an ultraviolet filter built into the tempered glass that is around the tube.
- 3). Compare the Kelvin temperature. Metal halide lights are available in many different color temperatures. Corals and other invertebrate animals, such as anemones, require a daylight bulb that has a high Kelvin rating, such as 20,000 degrees Kelvin. Marine fish, though, which are not dependent on light to manufacture food, can be housed under metal halide bulbs of a lower Kelvin rating, such as 10,000 degrees Kelvin. Check the Kelvin rating of the various metal halides, as lower ratings will give you a more yellow color, while the higher ratings will give a blue to purple color.
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