How to Convert From Metal Halide to Fluorescent

Reef aquarists worldwide continue to debate the costs and benefits of metal halide (MH) and T-5 fluorescent lighting. Switching to a T-5 system saves money. The bulbs last longer, are cheaper, and cost less to operate. Second, anything that can be grown under a metal halide setup can be grown under a T-5 setup. For hobbyists who choose to switch, the process is uncomplicated.

Things You'll Need

  • New T-5 lighting fixture
  • T-5 fluorescent bulbs
  • Old metal halide lighting fixture
  • Mounting/hanging kit
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Instructions

    • 1

      Research T-5 fluorescent light fixtures. There are many different fixtures for sale by different companies; good research will steer you away from poor brands and bad deals. Make sure the lights have individual reflectors to maximize light reaching the aquarium. Excellent units also have waterproof caps over light switches and a splash guard underneath the light bulbs. Fans or superior passive cooling designs are also important. The ballasts should be made by a reputable company. Positive customer reviews should not be overlooked.

    • 2

      Purchase the appropriate T-5 fixture. Convert between MH systems and T-5 systems like this: 150 watt MH systems are equitable to 4-bulb T-5 systems; 250 watt MH systems are equitable to 6-bulb T-5 systems; and 400 watt MH systems are equitable to 8-bulb T-5 systems. For example, if the aquarium's current lighting scheme is a pair of 250 watt MH fixtures, an appropriate replacement would be a 4-foot, 6-bulb T-5 system.

    • 3

      Purchase the T-5 light bulbs. Individual tastes in bulb color vary; choose a combination that will meet the coral's lighting requirements and provide a pleasing mix of colors. At the very least, half of the bulbs should be "white" and/or "yellow." These bulbs may also be marketed as midday, 10K and 7K bulbs, among other names. These bulbs provide the bulk of the light the coral needs for photosynthesis. The other bulb choices, marketed as blue, deep blue, actinic, and 20K, bring out a wide range of colors in the coral. These bulbs are what make the coral look "pretty."

    • 4

      Assemble the new lights in the new fixture. Most aquarists will stagger the white bulbs with blue bulbs to spread the color evenly throughout the aquarium.

    • 5

      Remove the old MH fixture. Try to do this in the morning, or before the lights have been turned on for the day. This avoids any interruptions to the coral's normal biological rhythms.

    • 6

      Install the new light fixture. The distance from the bulbs to the water's surface should remain unchanged from the old fixture. Follow the instructions for mounting or hanging the fixture. How the fixture will be supported is an aesthetic decision and won't affect the functionality of the tank.