Metal Halide

lamps are the most powerful lighting currently available to the reef hobby. These lamps come in 70, 150, 175, 250, 400 watt versions and provide the most output in comparison to their size. These lamps are also the hottest running lamp (literally, they are hot!) and will require a ventilation system to keep tank temperatures from rising. These lamps can commonly be found in industrial setting and sports fields in arrays of 10 to 15 fixtures together on top of a large pole and can light up a whole field in the middle of the night. These lamps operate by passing an electrical arc through a mixture of pressurized gasses, namely argon, mercury and a variety of metal halide type gasses, thus the name metal halide lamp.

Start-up and Behaviors:
Metal Halide lamps have a start up period. When the bulbs is at room temperature and is turned on it takes time for the lamp to warm up and produce its correct Kelvin temperature color and brightness. The initial start of the arc inside the lamp can take a few seconds and the warm up period after that may take up to 5 minutes before the correct color is emitted by the lamp. If power is cut off to the light, after or during the start-up phase a 5 to 10 minute cool down period will take place preventing re-striking of the arc. After this you should wait a full 10 minutes before trying to restart the lamp.

Old Lamp Behavior:
When a metal halide needs to be replaced it will show discoloration of its emitted light, meaning if you bought a 10,000K colored bulb, it may be producing a lower or different Kelvin color, resulting in discoloration of the light emitted. If the lamp is very old it may cycle once the lamp is turned on it can start at a low voltage but once it heats up more and more voltage will be required to keep the arc lit. Eventually the voltage required to keep the arc lit will be more than the electronic ballast can provide resulting in the lamp turning off, cooling down and restarting, or cycling.
Any metal halide should be turned off for at least 15 minutes during a 7 day period if used continuously. Metal Halides should be replaced every 6 to 18 months or as the manufacturer suggests.
According to Hamilton Technology these are the recommended tank depths for certain wattage Metal Halide Bulbs. Metal Halide bulbs are the best lights for deep tanks because other lights cannot penetrate as deep into water as these lights.

Mogul based lamps are simple lamps with the screw type base commonly found in incandescent household light bulbs. The base is not the same diameter and by no means should be put into a typical household lamp.

Single Ended bulbs only have prongs on one end.

Double Ended metal halides are similar to floor shop lights. Double ended means the lamp itself is fixed into the socket by both ends and not just one, a single ended style bulb would be attached to the socket with only one side.