Aquarium Components: Lighting
Aquarium lighting is important for tank aesthetics and for overall fish and plant health. The type of lighting required for an aquarium depends greatly on the fish and plants in the system. Any aquarium planning and budget should allow for the appropriate lighting needed for the tank inhabitants. Although natural sunlight may seem like the easiest way of illuminating an aquarium, intensity and duration are difficult to control and are often insufficient. These factors, however, are easily manipulated with artificial lighting and the use of a simple timer.
Lighting spectrum is commonly measured in units of degrees Kelvin (K). Light intensity is generally measured in watts, with higher watts providing more intense lights. Natural sunlight at noon has a spectrum of approximately 5500 K and is considered full spectrum since it contains all color wavelengths (red, orange, yellow, green, blue and violet). As light passes through water, the shorter wavelengths of red and orange are absorbed by the water within about the first 15 feet of depth. As the water becomes deeper, successively longer wavelengths of yellow and green are absorbed until finally only the blue and violet spectrums remain. Determination of what spectrum of light an organism requires in an aquarium is based on what spectrum of light it would receive in its natural environment (e.g., many corals receive only the blue end of the lighting spectrum in nature and, thus, this spectrum should be replicated in the saltwater aquarium).
Two main types of lighting are used by freshwater aquarists: fluorescent and incandescent. Fluorescent lights are gas-filled tubes of various lengths with pins on each end of the tube which connect into the lamp fittings. Incandescent bulbs are individual glass bulbs typically used for general household purpose.
Aquariums containing only freshwater fish have, in general, less specific lighting requirements than those containing plants or saltwater fish and invertebrates. As long as the lighting is aesthetically pleasing to the observer and the lighting pattern mimics a general day and night routine, lighting for freshwater fish tanks can be kept relatively simple and inexpensive. Most fluorescent bulbs that provide 1 to 2 watts per gallon are sufficient.
For aquariums with live plants, lighting demands are more specific. Plants require light for photosynthesis, a process by which plants use the light energy to produce food and oxygen from carbon dioxide and water. Plants will not survive in the aquarium if appropriate lighting for photosynthesis not provided. Because this light energy comes from sunlight in nature, full spectrum lighting must be provided in an aquarium to simulate this environment. A 12-hour light duration can be easily manipulated by use of a timer. Since intensity of this light is also important, bulbs should be changed on a regular basis (generally about every six months if on a 12-hour cycle) since the intensity of fluorescent light bulbs degrades over time, long before they "burn out." With the exception of very deep tanks, 1.5 to 2 watts of full-spectrum lighting per gallon should be sufficient for most planted aquariums.