PAR stands for "photosynthetically available (or active) radiation. It is a measure that already accounts for wavelengths, so extra consideration of wavelengths serves no purpose. Other measures, like wattage, lux, and lumens account for all visible light, not the photosynthetic range. A broader range of wavelengths within photosynthetic range are optimal, since that allows the maximum amount of energy for the corals as possible (even though for chlorophyll, the greatest spikes are in the red and blue regions). They have lots of other accessory pigments that allow them to take advantage of this. This, of course, depends upon the coral, collection spot, etc., but by and large, this is the ideal. PAR only accounts for photosynthesis, not aesthetics, though. That is where some people may not like it, since it is not always pleasing to the eye. Overall, though, blue light isn't correlated to coral growth.
I believe you missed the point completely.
http://www.advancedaquarist.com/2009/5/aafeature
Over 50% of zooxanthellae are reproducing (that is, in mitosis) at Hour 23 when maintained under 'pure' blue light for 12 hours. Lamps were off between Hours 12 and 24. After Wang et al., 2008.
Isn't A Large Dosage of Red Light Unnatural to Zooxanthellae?
Yes, in many cases. Since red light is rapidly absorbed by the water column, corals inhabiting depths of more than just a few meters do not receive a lot of red light. In aquaria, we desire some red light in order to observe the sometimes gaudy coloration of fishes and invertebrates. Obviously, many corals thrive in these conditions and it is difficult to state that small amounts of red light have any lasting, truly negative effects.
However, the evidence continues to mount that 'strong' red light can have detrimental effects, if even temporarily, on corals and other photosynthetic invertebrates. The effects of 'pure' blue, red, and infrared wavelengths have been examined individually and in combination. The results strongly suggest that 'pure' red light (at ~660 nm) can inhibit zooxanthellae reproduction rates.
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