is much cheaper per watt, especially in the long run with the multiple T-5 bulbs being replaced, to use an equivalent metal halide light setup over a T-5 setup if such high light output is required. All types of fluorescent lighting offer the same efficiency in lumens per watt; it is the shape of the bulb and reflectors that makes their overall outputs different. Metal halide Metal halide lights are generally the highest output lighting commercially available. They produce about 90-100 lumens per watt of power. This is roughly the same as fluorescent. The improvement with metal halides is that they concentrate this light output into a very small space, whereas fluorescent lights evenly illuminate the entire aquarium. This is often referred to as point source lighting, and is what causes the rippling visual effect on many advanced aquarium setups. This concentration of light output increases the intensity, allowing metal halide lamps to penetrate light to even the very bottom levels of most aquariums. Metal halides are available in many color temperatures, from 6500 K up to 20,000 K, though bulbs as high as 50,000 K are occasionally found. The downsides of metal halide lighting are the initial cost and the heat produced. Most metal halide fixtures are more expensive than fluorescent systems, but are required for some reef setups. Halide lamps concentrate heat as well as light output. The surface of an operating lamp becomes hot enough to cause second or third degree burns instantly, so this lighting technology must be used with caution. The heat produced can also warm the aquarium to unacceptable levels, possibly necessitating the use of a chiller for certain aquarium setups. LED The most recent addition to the list of aquarium lighting technologies is LED lighting. These have the potential to be much more efficient than any other technology, but are not fully developed. LEDs have the advantage of point source lighting, but are also adjustable to most power levels. This allows for more advanced lighting schedules, the simulation of cloud cover, or even lightning storms. So far, LEDs have found use mainly as lunar lighting in commercial products. Reef-keeping enthusiasts have begun to build their own LED light fixtures as well. Debate over their effectiveness towards coral is still inconclusive, particularly with respect to their ability to give off UV radiation, critical to obtaining a vibrant array of colors that most people interested