Photosynthetic pigments in the zooxanthellal cells carry out the collection of the light energy, such that they efficiently absorb light in the 400 to 700 nm range. The zooxanthellae contain various types of pigments: chlorophyll a, chlorophyll c and the carotenoids, such as Beta carotene, peridinnine and dinoxanthines. The pigments in the cells will absorb different wavelengths with different efficiencies. The absorption spectrum for zooxanthellae has been shown to have a broad peak in the 400 to 500 nm waveband (blue-green) and a narrow peak in the 650 to 700 (red) waveband.
Although it has not been proven that all coloration in corals is due to these UV protecting pigments, the practice of adding UV (or increasing UV) in the reef aquarium should be generally avoided, because it is likely to cause more harm than good.
Taken from your link.
http://www.animalnetwork.com/fish2/aqfm/19...s/2/default.asp