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").
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.
In my own experience, three suitable tubes for fish-only tanks or tanks containing plants with a low light requirement are: Hagen's Aquaglo, Arcadia's Tropical tube and Interpet's Beauty tube. These give the aquarium a 'warmer' appearance than some higher intensity 'white' lights, which can give a bleached-out look.
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 and Hagen's Floraglo and Powerglo.
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" 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.
