The first thing to consider about lighting up reef tanks is how much light you will be needing. The amount of light depends in a major way on the types of corals you are using in the tank. If your corals are photosensitive, then you will certainly need more light. Photosensitive corals can even die in the absence of proper lighting. Reef lighting must be ideally 4 to 6 watts per gallon if the tank houses mostly low light sensitivity coral, but it must be up to 10 watts per gallon if the coral is highly light sensitive. At the same time, the depth of the tank is also to be taken into account. Since all kinds of aquarium reef lighting are placed on top of the tank, their intensity will decrease as the light travels downwards. That is why taller reef tanks must have more intense lights than the squat ones.
The most popular kinds of lighting available for reef tanks are the fluorescent tubes. The VHO (Very High Output) fluorescent tubes are the most commonly used. These tubes produce light that is very close to natural light, and hence they are well suited to reef tanks. They produce very good intensities too (110 watts per 4 feet), which make them an economical choice. The VHO fluorescent tubes spread the light very evenly within the tank, which is good for temperature distribution. VHO fluorescent tubes are available in two natural colors - the full spectrum white (also known as the daylight tubes) that imitates sunlight and the actinic blue that closely resembles the bluish color of the ocean bottom. It is a good idea to buy a reef light that is a mixture of 50% of spectrum and 50% of actinic blue (such mixture lights are available).
For those who do not mind spending a few extra dollars on their reef tank lighting, the power compact fluorescent lights are the best options. These are fluorescent tubes that are bent several times and attached to a power source from only one end. The advantage of these lights is that they occupy a very small space within the tank, but give better light than the VHO fluorescent lights do. A 55-watt power compact fluorescent light will produce as much light as a 95 watt VHO fluorescent light. They are also power saving, and work for a very long time.
Another option is to go for the metal halide lights. Metal halide lights are good at throwing light in the reef tank, but they are not good for distributing light within the tank. Due to this reason, the tank can get hot due to inadequate temperature distribution. However, metal halide lights are good for prohibiting the growth of algae within the tank. The metal halide lights are the cheapest among the different form of reef lighting.
