Lighting in General
Light bulbs are more properly termed lamps. While your lighting choices are significant no matter what type of marine animals you are caring for, the proper quality of light is especially important to those who keep marine invertebrates.
Hard corals are, in general, the most sensitive of the invertebrates in terms of their need for specific light wavelengths. These and other invertebrates often rely upon simple algae known as zooxanthella for their food supply. These algae are extremely sensitive and will not grow unless provided with light of a suitable intensity and wavelength.
Few specifics are known concerning the light requirements of most aquatic animals. You should, therefore, err on the side of caution and provide full-spectrum light in natural cycles. The absence of such may help explain the poor captive breeding records of many creatures.
Those seeking to keep freshwater or marine fish and not invertebrates still need to be concerned about light, but less so. Although intensity and wavelength will not likely be as important as it is for marine invertebrates, fish certainly do best when provided with a lighting regime that approximates that of their natural habitat. As a safeguard, natural photoperiods should be provided if breeding is desired.
