Most aquarium corals contain within their tissue the symbiotic algae called zooxanthellae. It is these zooxanthellae that require light to perform photosynthesis and in turn produce simple sugars that the corals utilize for food. Therefore, the simple answer to light is to provide enough to maintain a thriving population of zooxanthellae in a corals tissue.
Intensity
Corals such as the Mushroom Coral and Coral Polyps require very little light to thrive.
Acropora Coral, Brain coral, Bubble Coral, Elegance Coral, Cup Coral, Torch Coral, Trumpet Coral can require substantially more intensity to thrive.
Color Rendering Index (CRI)
This is a measure of the ability of a light source to reproduce the colors of various objects being lit by the source. Range is 0-100.
Lamps are compared to daylight color samples and an average of their perceived color performance is given in CRI.
Photosynthetically Active Radiation (PAR)
designates the spectral range of solar light from 400 to 700 nanometers that is useful to terrestrial plants in the process of photosynthesis.
