Sanjay,
I wanted to pick your brain for a second (not Hannibal style...dont worry).
There are many out there that believe that 'PAR is PAR is PAR'...and that is all they consider when picking out bulbs for coral growth (besides looks). So according to them, coral growth with a yellower bulb woud be just as good as a bluer bulb...just as long as the PAR is the same. I just dont find this to be true...
In plants, red spectrums are for budding, and blue for growth...with green being reflected. In many cyanos, they feed off of IR so they dont have to compete with other species. I theorize that corals use the blue spectrum almost 100% and have little use for other spectrums (or access). Being that corals have less and less exposure to red spectrums as the depth in the ocean increases, warmer light would be an unlikely necessity or of possible use. Red pigments are used as a camoflage if nothing else...by corals and fish alike. Green spectrums are as useless to most any photosynthetic creature...no matter if they are land-plants or one of the 14 some-odd symbiotic cells being researched.
Many proponents of the 'PAR is PAR and thats all that matters to a coral' cite the Iwasaki 6500K as their main example. But when you look at the spectral graph, its easy to see why its a great grower. It contains just as much, if not more 420 and 450nm range light as a 10,000K...we just dont see it because it also has lots of green and warmer spectrums as well covering the bluer light up.
Where might warmer light come in? Well... In personal experience, I have 'overexposed' corals to the point that they brown out and stop growing. But only with 10,000K bulbs. OTOH, I have put two 400watt 20,000Ks (Radium and XM) over a 30breeder, and the corals do not brown out, and they grow like weeds as long as I keep the calcium coming. Coral 'farmers' have long touted the 1000watt 20,000K as the ultimate coral bulb...and despite the fact it might be used only 12" away from the coral...the coral doesnt brown out.
IMO, warmer spectrums tell the corals when to stop growing and 'brown out'. Why? Well, as a coral approaches the surface, the warmer specrtums increase. It would be in a corals best interest to stop growing before it ends up growing out of the water. It would also be in its best interest to start reflecting more light as it gets into shallower areas by turning brown in case of any UV. Well, Im not for sure on this...just a guess.
But the blue light part I am. I propose that the only real important spectrums for any bulb are in the 400-500nm range (blue). Is there a way to take readings from your equipment to compare the PAR's from just the 400-500nm range? This would level the playing field between 20,000Ks and 10,000Ks...which seems likely. I have gone from 10,000K bulbs to 20,000K bulbs with half the output, yet seen faster coral growth...all other parameters kept the same.
I wonder if in your research what your opinion would be on measuring the relative PAR's for just the 400-500nm spectrums. What do you think?
Also, is there a way to experiment with this? I was thinking of trying to find two bulbs...one of entire 420 and 450nm outputs...perhaps a T5 fixture with blue and actinic only... and then in another connected tank, use some bulbs that have almost completely red/yellow light but of equal PAR. Halogens maybe? How could this be done?
I would like to see once and for all if warmer light means anything to our reefs. If not, then perhaps a second PAR reading covering only bluer spectrums would be more important to us.
