Aquarium lighting

Aquarium lighting describes any type of light that is used to illuminate an aquarium tank or in some instances, such as with reef aquariums, support the life contained within.

Freshwater

Freshwater aquarium lighting often comes in two forms; one is a screw-in style incandescent bulb and the other is normal output fluorescent lighting. Screw-in compact fluorescent lighting is also used in freshwater aquaria since it provides brighter light output than traditional screw-in style bulbs.

More demanding freshwater set-ups, such as planted freshwater aquariums, may require stronger light sources. Compact fluorescent bulbs, high output T5 bulbs or metal halide lamps are often used over such aquariums to encourage plant growth. While these lights can provide a better spectrum than traditional ones, they often use more electricity and have a high heat output.

Reef

The reef aquarium field is where aquarium lighting varies the greatest. Some reef aquarium keepers use VHO (Very High Output) fluorescent tubes, compact fluorescent lighting, and metal halid lighting since they provide much brighter light than average fluorescent bulbs and come in a variety of spectrums. Reef keepers often opt for light of varying spectrum. Since many corals require a deep blue or actinic spectrum of light (7500k) to thrive many aquarists must supplement traditional white light with light of this color. Also popular with reef keepers is T5 High Output fluorescent bulbs. These bulbs are thinner than traditional T8 bulbs and provide a much brighter, more powerful light.

Another light source in reef aquariums today is metal halide lighting. These high output lights closely recreate the shimmering effect of bright tropical sun over a patch of coral reef. These lights can create the best true spectrum output. Metal halide bulbs come in a variety of spectra from 5000k on up to true 20,000k and allow for a variety of light hungry corals to survive under them. Many aquarists will use metal halide bulbs in conjunction with either power compact fluorescents or T5 fluorescents since halide lighting does not have the overall balanced effect of other light types. While very useful to reef aquarium keepers, halide lighting also uses a lot of electricity (150-400 watts being common)and produces copious amounts of heat. Most reef keepers mount halide bulbs at least one foot above their tank and some, due to the lights' heat output have had to add chillers to keep aquarium water cool.

Many light fixtures come as all-in-one units with light for both daylight hours and nighttime viewing. LED lamps of 3/4 to 2 watts can be implemented to come on at night, simulating the glow of the moon over the tank. All in one fixtures require large fans to cool the bulbs and achieve maximum light efficiency. LED lighting is also becoming more common for not only lunar lighting but also to simulate daylight conditions, LED's have a higher initial cost than other lighting sources but utilize much less energy. They are also dimmable. LEDs produce a very narrow color spectrum that is limited to a narrow band of wavelengths. For this reason an array of different colored LEDs is required to be used in combination to simulate spectral coverage that is suitable for coral growth. Early adopters of pure LED based systems have reported that the limited color spectrum provided by LEDs may not produce optimal coral growth.