With the exception of a few species, fish do not require special light for health. In fish only tanks, one would want to provide lighting that minimizes the growth of algae while maximizing the color of the fish. In tanks containing coral and plants, the spectral distribution of the light becomes a factor. For the coral and plants to survive, there must be adequate amounts of light in the blue and red regions of the spectrum to allow photosynthesis. The light should also be of sufficient intensity for plant respiration. The amount of light should be tempered, however, as too much light could startle the fish. Typical setups have alternating 12 hour periods of light and dark. To prevent fish startling, a blue actinic lamp is used before the more white light source is turned on.