It's actually interesting what has happened with LEDs. We started with little info and very few people understood said info. Now we are basically flooded with so much info that we can't absorb it all. A lot of misinfo as well. I have done extensive reading. I'm a recent biology grad and have had a decent amount of physics. As I understand it there are a couple of key issues with LEDs.
1) even the LED systems with multiple colored diodes have narrow spectrums. This actually is what people love about LEDs. A blue led only produces blue light. For those who haven't had physics think of it like this. There are two ways to get green light in a tank. 1 is to have just a green led producing 500nm light. The other way is to have 1 blue led and one yellow led. To the human eye this is also green. However to your coral they much prefer the blue yellow combo.
Really? I think blue is a yes, but I've never read or heard any scientist say corals like or need yellow spectrum. A little bit of red for the zooxanthellae to do photo synthesis with, but not yellow. What is your source for that data? But your blue & yellow making green for our eyes and still being blue and yellow for the corals is spot on! This essentially is how a metal halide does it. It combines many many colors to make an overall look that is blueish or 20k.
2) now to counter that last point. In the ocean colors other then blue are filtered out by water by around 36" in depth. Really the first 8" of your tank take most color out.
Whoa! I hope you mean 36 feet and not 36 inches. And how in the world do you come up with,"the first 8 inches of your tank take most color out." That isn't even remotely accurate. Have you ever been scuba diving? Most colors of the spectrum get down about at least 5 feet and many make it down 20 feet or more. So there are two different things going on here. First, most coral in the wild is adapted to mostly blue light because most coral lives more than a couple feet under water. Second even if you put a ton of color in your LEDs most is filtered out by 8".
The reason most corals want blue light isn't really because that is what they are adapted to, it's because the zooxanthellae they grow and consume use chlorophyll for photo synthesis and that process is mostly dependent on blue spectrum.
What I find funny is how willing the led companies fuel the misinformation fire.
I don't think most do it on purpose. But you are right in that most led fixture manufacturers are just manufacturers and don't do much if any science. Especially the really cheap Chinese junk that gets sold on E-bay and Aliexpress. Just look at how many fixtures are still being sold that have 1:1 blue to white rayios and then add in red and green thinking that makes them better! If you have a 1:1 or even a 2:1 blue to white ratio, you really don't need red or greed leds. The white leds already make more than enough red and green. And green really isn't all that important to the coral, it's zooxanthellae, or photo synthesis either. Maybe if you go as far as a 3:1 or 4:1 ratio, you won't have enough red spectrum being emitted from the white leds and a red led or two may be useful. I mean they must consult with people who are biologists and physicists who tell them far more than what I just said. But if reefers said its actually microwaves that make my corals grow you would have the new " Maxspect razerwave that gives your corals the microwaves they need" even though science would undoubtedly disagree.
I think you are going a bit overboard here. I have gone back and forth on UV light being a good thing in a reef tank. UV light is nasty stuff and usually is what distinguishes shallow water and deeper water species. Ie you can only be shallow water if you are adapted to dealing with the uv. When I say UV I'm talking 375 nm and below. 400 is probably not harmful.
I agree with you about UV and that 400nm really isn't harmful (I'm not sure it's even considered UV).
There is my 2 cents
. Cheers
