Riddle's conclusion is Red light limits coral growth.
Going through his data I would differ to that conclusion and say that excessive red light limits growth. If your obverseve all the lights they used did produce red light. While the 20,000K produced the best growth it still produced more than 1/3 of the amount of red light as the 10,000K bulb produced.
What I also find instring is that the 5,500K bulbs actualy gave better growth than the 10,000K bulbs even though the 20,000K gave the best growth.
Having been trained in Six Sigma and worked with it considerably over 15 years I would have looked at a completly different way to make these determinations. Mainly using light two sepeate light sources ine prodicing light in the 417nm to 485 nm blue range and a second source with the 625 nm to 655 nm range red range. Then keeping the known major blue light constant on all samples I would have each of the sanples exposed to different intesities of red light including one sample where where red red light was elininated.
Riddle said:
The work of Schlacher, Stark and Fischer is important, and a great stride in improving our understanding of the effects of artificial light on coral growth and survival.
However, we should remember that these results are from experiments with a single species collected from a specific depth and geographical location. This information may, or may not, be applicable to other corals. Clearly, more research is needed, but this does not lessen the importance of these researchers' results.
In addition, we should also note that Kelvin ratings are a poor indicator of true spectral quality - that is, it is a mistake to judge the 'warmness' or 'coolness' of a lamp when Kelvin is based on measurements made of lamps possessing 'spiky' line spectra such as mercury vapor or metal halides.
Noting that they used on one particular coral I would also try these tests and various corals. It is known that various corals have different ratios of various chemicals working within them and there fore what may be true for one coral may not be neccessarly true for another coral.
Looking at some of the LED lighting forums I see loads of stories where one particular set of LED lights are working fantastic for some people howver for others they are having complaints especialy in color shifts. These usualy turn out to be different corals that the individuals are working with. So this further makes me suggest that the lighting that is ideal for coral A might not be ideal for coral B.
Having worked considerably with LEDs they generaly produce narrower bands of and therefore I think we are seeing these more readily in the LED lighted tanks than the HO T-5 lighted or Metal Hide lited tanks that by nature produce brawder band witdths.
Keep in mind that even the plots you displayed for Chlorphyll A the intensity of the blue light required is roughly 50% of the red light, and for Chlorophyll B roughly 25%. Yet when you have a 6,500K bulb with a CRI of 100 the output
of red and blue is roughly equal.
Therefore it is my belief that some red light is still an important element however I will agree that an excessive amount of red light can easily cause issues. The question being how much red is benificial and how much is detrimental.
Remember in your posts Grim you often recommend the purple + bulbs. These pruple plus bulbs are virtualy bulbs with a secondary peak at 615nm in the red spectrum , the aqua blue special having its third peak at about 610 nm in the red spectrum, and the GE 6,500K bulb having a very strong and broad peak in the 610 nm range. In realate would you recommend a taqnk with only Blue = bulbs peaking at 450 nm and Atinic Bulbs peaking at 420 nm without any red wavelenghts at all?
In my experience with an 8 bulb system having one 6,500K bulb in my system did give the best coral growth when balanced with all the other bulbs giving strong light in the 410 to 460 nm range. However I did not like the overall color remdition from this bulb which appeared to yellow for my tastes and I also suspected was delivering to much light in the 565nm range which has been proven that Cyno Bacteria thrive at.
