An Introduction to Metal Halide Reef Aquarium Lighting
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Why Metal Halide Lighting?
Simply put, there is no option for lighting your reef aquarium that is currently available offering as many benefits as metal halide lighting. The preferred lighting for SPS reef tanks the world over, metal halides feature significantly higher PAR (photosynthetically available radiation) than other lighting options; such as VHO (very high output flourescent), PC (power compact flourescent) and the latest entry T5 (narrow bulb, medium output flourescent). This translates into faster growth, brighter colors and overall improved health for photosynthetic organisms. While it is certainly true that there will always be successes with other lighting types, the use of metal halide lighting on reef tanks is undoubtedly the best bet to ensuring success.
Most users of metal halide lighting opt to accentuate the color spectrum of the bulbs by combining them with either VHO or T5 actinic flourescent lighting. Actinic lighting is extremely blue in color, a look that is pleasant to the eye and brings out the luminescence of certain corals and clams.
Metal halide lighting is available in several different types of systems. Metal halide pendants are most popular with reef aquarium users opting not to use a canopy to cover their tank. The primary advantage of this method is temperature control, with an open top allowing maximum air exchange to keep reef tanks cool (particularly an issue with reef aquariums not using expensive chillers). Pendants are often suspended from the ceiling or brackets mounted securely to the wall behind the aquarium.
Pre-assembled metal halide lighting systems are available from many manufacturers that offer an easy solution to reef aquarium lighting; by combining metal halide light bulbs, actinic light bulbs, all necessary ballasts and electronic wiring and usually cooling fans, into a single attractive box to place over the aquarium. These solutions range dramatically in price and quality. These systems are most recommended for reef aquarists who don't tinker, as they do not offer the easy upgrades and updates that the other systems do.
The most popular lighting systems, as well as the most flexible systems, are called retrofit metal halide lighting. Retrofit systems are comprised of a combination of several components; a metal halide ballast, desired spectrum of metal halide bulbs, reflectors and wiring. Many reef hobbyists with canopies over their tanks opt for retrofit lighting solutions, as they offer the greatest flexibility and can be designed to fit within more limited spaces.