I do agree with this - a lot of the rarer SPS come from shallower waters with a lot of UV hitting them, so they have an extra thick 'clear coat' to protect and makes them stunning in coloration, but there are also a lot of corals that may not be able to handle the levels of UV needed to keep the colors in those rarer corals, and side-by-side may not do well. It's a fine line to walk, for sure, and I always recommend to stay away from them (as most people adding them don't know the reasoning behind it).
I agree with most of your statement. I tried nuetral whites and had decent results, but not as good as with cool whites and warm whites mixed, like I said, best of both worlds. Other than that, I agree with you on the violets, royal blues, and deep reds. I did some research recently, and the 590nm spectrum will excite the reds in some corals, so that is a big reason I like to incorporate warm whites, they are pretty heavy in the yellows and oranges. I tried it out with some pure 595nm, and it worked pretty well, but was a little too red looking overall, so the warm whites work nicely, unless, like the UV LEDs, the 595s are dimmed separately.I'm about to step on a loooooot of toes here.
I'd expect no less from a vendor who only sells fixtures using cool white LEDs.
Without the additional red spectrum, not only does the tank just look anemic, but you start to lose non-fluorescent colors. That's great if all you want is that glow from your corals that have green fluorescent proteins, or a few reds that have red fluorescent proteins, but a lot of oranges, yellows, pinks just don't show up because that light simply isn't present for them to reflect.
Comparing any array containing only cool whites to an array based on Bridgelux BXRA or Rebel ES neutrals in the 4-5000k range will be absolutely no contest in color and depth while still retaining the same superior actinic response provided by royal blue LEDs.
As for their PAR value, the entire spectra of the white LED adds to the PAR value. PAR is next to useless as a metric because it simply the total quanity of light emitted - I can build an array that sends out 500 PAR at 24" yet will not grow coral, as the light will be solely composed of 530nm light, a spectra in which little to no photosynthetic activity occurs in corals.
A cool white LED does not emit as much photosynthetically active radiation (PAR) or photosynthetically usable radiation (PUR) as a royal blue LED does (within the same family, of course - comparing an XT-E cool white at 1000ma to a Bridgelux BXCE royal at 700ma, for instance, isn't a valid comparison), simply because a white LED is a royal blue LED with phosphors applied to it - so you wouldn't be able to a 1600mW royal blue chip, apply a phosphor, and still have 1600mW of output in the royal blue spectra.
Taking into account that a cool white array typically uses a 1:1 ratio of cool white to royal blue, and a neutral white array typically uses a 1:2 ratio of neutral white to royal blue, an array based on neutral white will have the same PAR using less total LEDs, or more PAR if using the same amount.
Now, to address your issues with colored LEDs.
Note the massive spikes in red. Despite numerous tests that have been performed (like the ones you linked to earlier), deep red does not bleach coral, at least not in the quantities we DIY'ers recommend. If you blast a coral with too much light of any wavelength it will bleach, and in particular to a wavelength that the coral has no protection built up to.
Green is wholly unnecessary. All white LEDs contain far too much green as it is. What they are lacking is cyan, which is pretty essential in color rendition.
Now violet - this is the 'meat' of photosynthesis. You see that graph above, how it drops sharply after 430nm? If you load up a tank with royal blue chips at 455nm or higher, are you really hitting chlorophyll a, the primary driver of photosynthesis in almost all corals, hard? Nope. It takes violet LEDs to do that. Chlorophyll C1 and C2 are different and can effectively use that 450ish-nm light, no sweat. However, chlorophyll c is present at 1/10 the numbers of chlorophyll a. (note that chlorophyll b, whose primary photosynthetic peak is at 450nm, is not present in zooxanthellae)
Corals are subjected to immense amounts of violet light in the wild: Feature Article: Light in the Reef Aquaria — Advanced Aquarist | Aquarist Magazine and Blog So if violet is the primary driver of photosynthetic activity, why is it unnecessary again?
Am I saying that royal blue and cool white LEDs cannot grow coral? Absolutely not. That has been proven time and time again. Is it optimal for both color and growth? No.
Back to the subject of neutral whites. Some 'light' reading:
LED Aesthetics: What do you really think of your color? - Lighting Forum - Nano-Reef.com Forums
The 'Evil Cluster' revisited - Lighting Forum - Nano-Reef.com Forums
A quote from the OP of that thread, blasterman:
The people in those threads are partially (if not wholly) the driving force behind the LED arrays we have now.
I think I hit everything I wanted to, but I'm sure I missed something.
The new Radion includes some amber LEDs (they call them yellow, but 590ish-nm is amber ;) ) and combined with their hyper red, true green, makes for a complex array - when they could just use warm/neutral whites and have better color without having a light show, though their optics do help to mitigate that slightly.
Do keep us updated on that - I know of a lot of people that go to test something and then in a few months have gone off the radar without sharing their results. ;)
Are you talking about my thread on photosynthesis? Violet spectrum, specifically 430nm, is the main driving force to photosynthesis in corals, as that is the peak of chlorophyll a, and it drops off sharply after that. I'd say that if you matched the output in mW of violet LEDs to what we use with royal blue LEDs that you would get much more growth. It wouldn't look as good (since we can't see the violet light very well), but dang, would everything fluorescent just GLOW! ;)
Go back and look at the spectrograph in post 19. Violet and RB alone would probably allow many corals to do quite well, probably better than RB/white. Violet is an important part of the spectrum and as availability of violet LEDs has grown, so has their use. My main fixture uses 10 violet LEDs out of 70 (66 and 4 moonlights), in hindsight, I wish I'd used more of them.
CRI doesn't really apply to what we use LEDs for. CRI is based on a blackbody radiator, so it really isn't helpful to us the way it would be to other scenarios where spectrum isn't as important.
I was the one who designed his array. ;)
Thank you.
And? They aren't bright, but that's because our eyes cannot see the light they output. Our eyes are absolutely terrible at seeing blue light, which is why green and red LEDs stand out in an array sometimes. A violet LED will make a PAR meter light up, and once you correct for the margin of error, you'll see that they emit a ton of PUR, as it sits on the most photosynthetically active spectrum in photosynthesis.
Again, it's not just about color. And just because they are SemiLEDs brand doesn't mean that they're all that. It depends on the bin, spectra, and radiance.
Have you actually looked at the 'experiment' performed where Dana Riddle killed part of a coral using a red LED placed 1/4" away from it? Of course it was going to bleach. Giving 100 micromols of PAR in solely 660nm will kill any coral that is not grown in shallow water in nature, and even then may still hurt it due to too much light.
It's actually 30 feet (10 meters). I have seen nothing to disprove that chlorophyll in corals is unable to absorb red light. Check out the PDF file in the first couple of paragraphs in this post: https://www.reef2reef.com/forums/eq...0170-lighting-spectra-photosynthesis-you.html
Who said anything about low PAR?
