Quote:
|
If the far red spectrum is unnecessary, then why add it.
|
Not critical for growth, but you need longer wavelengths for color. Cool white LEDs are enemic in orange and red, which is why their color sucks. If I did a side by side comparison of a LED light made with cool whites -vs- neutrals you'd throw rocks at the cool whites.
The aethestics issue aside, I have no idea why we're still debating about LEDs producing good, legitimate PAR. I've seen enough wildy growing SPS tanks under LEDs with a fraction the power of the halides being replaced to more than be convinced. Color might suck, but that's a different issue, and the Cree Cool-White cult won't change their mind anyways because they can't tell the difference between LED steet lights and reef lights as long PAR meters are pinging numbers at them.
Corals want deep blue light. Its just an evolutionary adjustment to growing under water. There is some debate about shallow water corals like Acropora that frequently grow into the air at low tide possibly being able to utilize warmer wavelengths, but evidence is sketchy. Some other evidence that an abundance of red light tells the coral 'Hey, moron, you're growing above water in a tidal zone, stop it."
LEDs are extremely efficient at producing far blue light in the 455nm range, and it's the one thing they do well. Last spring I did a test where I hit Acropora frags with single 3watt LEDs of various colors using 10 degree optics just to see what would happen. A cool white Cree R2, and Red and Green K2s had no effect on the Acros (miami orchid). However, a regular blue Cree caused the Acro to bleach badly in less than 36 hours. This was pretty much all I need to confirm that blue is action spectrum.
Biologists I've talked to seem to be mixed on where the maximum action spectrum is for zooxanthellae algae. Some say it rides with the clorophyll A line at around 440nm, and other say pretty much any strong blue spectrum is sufficient. Looking at Sanjay Joshi's spectral plots of Reef halides all show a common denominator, and that's massive amount of light at around 450nm. So, if I were a betting man, I'd say that spectral energy at 440-460nm is 'happy time' for corals. This confirms all the happy SPS tanks I've seen with LED
The need for blue deeper than LED royal blue (below 455nm or so) is sketchy. For aethestics, yes, by all means light deeper than what royal blue LEDs can generate looks really good because there are some 440nm reef lights out there, and they look fantastic. Is it required for better zooxanthellae growth? I just don't know, but it woulndn't seem so.
Quote:
|
If this is the case, why can't someone ask a manufacturer to do this to create the missing spectrum? It sems like this is the real answer because it obviously doesn't exist yet in the real world of LED lighting.
|
There ARE 440nm lights out there; I think Reef Brite or Sun Brite make them. PJR is running them on his SPS tank over at Michigan Reefers and his growth is nutz.
I screamed and yelled and finally got somebody to make some 10watt 445nm LEDs, and I'll be happy with my victory. However, as I've said in other thread, the DIY community is obsessed with Cree, and if Cree doesn't make 440nm LEDs then the reason is 440nm must suck.
The hole in the spectrum of white LEDs at around 485 isn't a concern of mine since this color would be a combination of Windex and green Lysol.
Quote:
|
Well, Look at the spectra of popular MH and T5 bulbs. You'll see that ~680nm peak almost every time
|
Where? I'm looking at Sanjay's graphs and don't see 680nm anywhere. Also, far red is very difficult for fluorescent phosphors or halides to produce, which is why high pressure sodiums are preferred for agriculture use. Also, at 30feet under the ocean you could probably count the number of 680nm photons penetrating that deep on one hand. Does it matter to an Acropora growing above the water on a reef? Maybe......
Last, I really, really am skeptical of readings from PAR meters because unless it's calibrated specifically for reef use it's feeding numbers likely not optimized for corals. Red light light is critical for dope and tomato growing, but doesn't mean much to corals. However, general use PAR meters are goign to key off of red light because that's their intended market.
This explains why I've seen some reefers get higher PAR numbers from white light LEDs than dedicated blues. The PAR meter is reading spectra that will grow a tomato plant, but not ideal for acropora. This is why I'm far more concerned about actual spectral plots than PAR readings.
In any respect, I give this thread a '10' on a scale of 1-10 because were actually talking about data and not brands.