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Aquarium Lighting
The lighting used in an aquarium is governed to a large extent by whether the tank is to contain live plants.
If the tank will not contain plants (or only plastic plants) then the light need only provide a means to
view the fish. The choice of lighting is then only governed by choosing a light which enhances the colours
of fish. A light intensity of around 10W per square foot of water surface area is sufficient for this
purpose (e.g. a 40W fluorescent tube for a tank with a base measuring 48x12").
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Fluorescent tubes are the most commonly used form of lighting in aquariums. They are available in a range
of sizes and colour spectrums to suit different tanks and applications. The "standard" fluorescent tube for aquarium use has
previously been the "T8" tube - meaning eight-eighths (8/8) of an inch or 1" diameter. In more recent years, T5 tubes that
are 5/8" diameter have become popular. These are generally brighter for a given length than T8 tubes, so are particularly popular for
taller tanks and planted tanks where more intense lighting is desired. They are now standard in many popular commercial tank brands.
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Fluorescent tubes suitable for fish-only tanks or tanks containing plants with a low light requirement are generally those
described as warm white. These include Hagen's Sunglo, Arcadia's Tropical tube, Interpet's Beauty tube (later renamed Community Daylight) and the Juwel Warm-Lite.
These give the aquarium a "warmer" appearance than some higher intensity "daylight" or "full spectrum" white lights, which can give a
bleached-out look in certain setups.
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Planted tanks need more light than fish only tanks, and the type of lighting becomes more important. The
light requirement of different plant species varies somewhat, but generally the light will need to be at
least double that recommended for a fish only tank, i.e. 20W per square foot of tank surface area. Light
requirements are also quoted per volume, e.g. 2W per gallon. A number of manufacturers produce fluorescent
tubes designed to provide maximum plant growth. These include Arcadia's Freshwater tube, Interpet's Triton
tube (later renamed Tropical Daylight), Hagen's Lifeglo and the Juwel Day-Lite.
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For heavily planted tanks, some may opt for metal halide or mercury vapour lights, which are normally
suspended above an open-top tank. These are able to punch light deeper than fluorescent tubing and are
therefore useful for tanks 24"/60cm or more high. It should be remembered that when higher intensity lighting
is employed to boost plant growth, it will be necessary to balance this with an adequate amount of
nutrients and CO2.
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One of the more recent changes in the lighting available for aquariums has been a move towards LED lighting. Although still relatively expensive,
LED lighting offers longer life, lower wattage (and hence running costs), compact designs and more flexibility - including such innovations as user-programmable
intensity and spectral output. LED's also offer "point source" lighting that gives a pleasant shimmer to the water (like metal halides) - an effect not
seen with the "flat" light from a fluorescent tube.
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