By Blane Perun
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Proper lighting is very important for the health and growth of corals in a reef aquarium. Technology in reef aquarium lighting has advanced a great deal and it is not difficult to find the right system for your reef aquarium environment.
The reason lighting is so important in reef aquariums is because of photosynthesis. Coral has to produce a thriving amount of zooxanthella in order to live. Zooxanthella is a symbiotic algae that inhabits the coral cells and produces energy. Without photosynthesis, the algae does not grow. Photosynthesis is a complicated process that occurs in nature where light produces simple sugars that the corals use for food. To keep this process going, proper light is crucial.
There are a couple of different options for lighting a reef aquarium, but the two most common sources are fluorescent tubes or metal halid lighting. Depending on the type of coral, you may need more or less light. Many corals need a deep blue or actinic spectrum of light which can be supplied by using a white bulb and a colored bulb. Regarding florescent bulbs, the T5 High Output bulbs are very popular. They provide a more powerful light than the T8 bulbs.
Metal halide lighting is also very popular for reef aquariums. Metal halide lighting mimics the shimmering effect of tropical sun that coral reacts very nicely to, as they would in nature. Metal halide lighting comes in bulbs with a varying amount of intensity from 5000k to 20,000k. They are very bright and produce a great amount of heat. Metal halide light users often keep the lights higher off the tank and use cooling methods so that the water is not overheated.
Metal halide light can be used with florescent bulbs as another lighting option. The users of metal halide light find that they use a great deal of electricity (150-400 watts per hour) so that is something to consider when setting up a reef aquarium. Some corals like the mushroom coral and coral polyps don’t require much light so the strength of metal halide lighting may not be necessary. However, on the other hand, most LPS and SPS corals require moderate to high levels of light therefore metal halide lighting may be useful.
Different light can be used for day and night. Most of the light fixtures for reef aquariums have fixtures that are good for both daylight hours and nighttime viewing. LED lamps, or light-emitting diodes, can be adjusted to shine differently at night versus the day. They are designed to mimic daylight conditions or moonlight providing a good environment for coral. LED’s may cost more up front, but they use less energy than the metal halide light options. They can also be more easily adjusted from high light to lower light. Unlike fluorescent bulbs, however, LEDs have a small spectrum of light options. For coral that need a differing color spectrum, LEDs may not be the best choice or they should be used in conjunction with other lights.