How to Compare Metal Halide Lighting

Metal halide bulbs have many positive characteristics. These bulbs have an average life of more than 10 times that of incandescent lights. Their output is similar to sunlight and they are available in numerous color temperatures, ranging from 2,700 to 20,000 degrees Kelvin. Metal halide lamps are compact and highly efficient, generating more lumens per watt than fluorescent or incandescent lights. Metal halide bulbs in the 20,000 degrees Kelvin-range are much sought after by marine aquarists, as they produce a blue light that is required by corals and anemones. The intense light produced by metal halides also creates glitter lines in the aquarium, which is very pleasing to view.

Things You'll Need

  • Assortment of single-ended metal halide bulbs of varying watts and color temperatures
  • Assortment of double-ended metal halide bulbs of varying watts and color temperatures
  • Assortment of ballasts to fit both single- and double-ended metal halide bulbs
  • Marine aquarium with both fish and invertebrate animals, such as corals
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Instructions

    • 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.