Corals and PAR...

[RaymondL]

As far as I'm told, corals make use of the blue wavelength of light - my confusion comes from the perspective of total PAR value - is coral growth and health dependent on the overall PAR provided by all light channels (ie. Violet, Purple, White, Cyan, etc), or is it mainly focused on just the blue light. One can have low PAR values on the blue channel, but in combination of other colors, yield the necessary PAR value(s) needed by the specific corals?

 

[mike550]

As far as I'm told, corals make use of the blue wavelength of light - my confusion comes from the perspective of total PAR value - is coral growth and health dependent on the overall PAR provided by all light channels (ie. Violet, Purple, White, Cyan, etc), or is it mainly focused on just the blue light. One can have low PAR values on the blue channel, but in combination of other colors, yield the necessary PAR value(s) needed by the specific corals?

So this is a really interesting question, and here is my very basic understanding of PAR in the context of your question.

PAR measures the amount of light in the 400nm to 700nm range because this is what is used for photosynthesis. It’s basically the full visible light spectrum. To your question if you can only measure PAR across the entire spectrum then to your point “white” light could have higher PAR than just the blue-violet portion. My sense is that if you tune your lights to emphasize the violet-blue range and keep the red, green, white portions low (think AB+ profile) then the PAR measurement will fairly measure the light intensity in the area that’s most important to coral growth.