Components of Metal Halide Lighting

For aquarium enthusiasts, adequate lighting is can be vital to the survival of their aquatic pets. Metal halide (MH) lights are but one of many choices available. While kits do exist which contain all of the elements in one package, you can assemble your own metal halide lighting, using a multitude of different components.

  1. Lamp

    • An MH light uses a two-envelope lamp that is composed of two parts: an outer bulb which filters out the ultraviolet radiation from the lamp and shields the inner envelope, and an arc tube. Using various metal halides, mercury and inert gas, these lights vary in wattage and color temperatures. The lamp itself consists of the bulb and the base it mounts onto.

    Ballast

    • The ballast provides the proper starting and operating voltages, and the current used to initiate and sustain the arc inside the lamp which creates the light. The ballast also acts as a limiter, as MH lights draw increasingly more current as they run. Ballasts come in a variety of types and should always be paired with an appropriately matching lamp.

    Socket

    • The socket holds the bulb and directs current into it to operate. The socket used for mounting a bulb in an MH light must be of the same size as the bulb and have threads that will properly screw together. There are a number of types of socket available, depending on the type of bulb being installed.

    Brackets

    • A bracket is used to hold the socket and attach it to the hood. The typical construction is relatively simple, consisting of little more than an L-shaped strip of aluminum with holes drilled for attaching the socket and hood.

    Wiring

    • Proper wiring is a must in an MH light. The type of wire used depends primarily on the light being installed. The wiring used comes in two types, stranded and solid, although stranded is used more often due to it's flexibility and durability.

    Fan

    • Proper ventilation is necessary to dissipate the heat generated by the light, preventing damage to the aquarium and injury to the corals. Fans can be mounted to suck air out or blow air in, but they typically are employed in tandem---one working in each flow direction to create an adequate air flow.

    Reflective Surfaces

    • Without a reflector, the light would lack direction. Reflectors come in a variety of types, from professionally made reflecting surfaces that may be shaped to get different effects to a lining on the hood surface itself. Do-it-yourself surfacing solutions include polished sheets of aluminum, white house paint and aluminum tape designed for duct work.

    Hood

    • This enclosure houses all the other components and mounts them over the tank. Typically, they are made or wood or another easy to shape material and custom built for individual aquariums. They are generally shaped like enclosed boxes, with hinged openings designed to allow access into the tank and to the lights themselves.