Cool or Warm LED's? Ideal balance of red and blue light??
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Old 02-13-2011, 11:40 PM   #1
Mxx
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Cool or Warm LED's? Ideal balance of red and blue light??


Which of these LED's is better for plants, the cool white or the warm white??



The warm white LED's have almost an equal amount of red light and blue light, while the cool white have about three times as much blue as red. What should the balance of red light and blue light ideally be?

At the moment I'm running a strip of warm white, a strip of cool white, and a 2 small wands of red LED's to try to reach a roughly equitable balance and fish color rendition which I'm happy with.

I'd read the following: Plants have two types of chlorophyll: A and B. Chlorophyll A absorbs light at 405 and 640 nm. Chlorophyll B has peak absorptions at 440 and 620 nm. Plant lamps are designed to emit light at red wavelengths to duplicate the light of the sun, but too much red color can cause aquatic plants to grow tall and thin. For best results, use a daylight (5000K) lamp in combination with an actinic white or actinic day lamp.

But I'd also seen statements elsewhere which use slightly different numbers, and it's obviously not as if plants only use a single wavelength of light. I'd also seen 420 mentioned as the peak absorption point for chlorophyll A, and that chlorophyll can use light from 400-550 nm and 650-700 nm.
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Old 02-14-2011, 12:17 AM   #2
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To add to that, here are some typical K and nm values I'd been seeing for LED's. (To convert back and forth between K and nm, divide 3,000,000 by the figure, apparently).

Cool White 8000K (as well as 5500K-10,000K)
Pure White 6000K (also known as xenon white)
Neutral White 4200K
Nature White 4000K
Warm White 3000-3300K
Red: 625-660 nm.
Green: 525 nm
Aqua: 505 nm
Blue 470 nm.
Pink 440 nm.
Violet 420 nm.
Ultraviolet LED's range from 380 nm to 405 nm.

Thus, to cover the spectrum at 405, 440, 640, and 620 for both chlorophyll A and B and thus to best suit your plants, you could use Red, Pink, and Ultraviolet LED's?

The low end of both warm white and even cool white still seem to be a bit to high for optimal plant growth. So it would still seem best to supplement white LED's with some ultraviolet LED's?

I'm not sure what that would do to your color rendition, but warm and cool LED's suffer a big drop in the 500 nm region of light, which could be supplemented with some aqua and some green. (That might not make your plants grow any better obviously, but might nevertheless help your color rendition).

I'd also bought an RGB LED strip to play with, but unfortunately it doesn't fit within the very tight slots I have for LED strips in my hood as it's a little wider.

And yes, these are your standard LED's that I'm talking about here. I wouldn't doubt that some more expensive ones such as CREE's perhaps might have better color rendition and PAR over the spectrum that plants use, but those are not the LED's that I'm asking about just now.
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Old 02-14-2011, 01:25 AM   #3
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Either will grow plants just fine, it really boils down to which color do you like staring at and even that wont matter much once you get used to it. If you really want to get fancy you can always use both!
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Old 02-14-2011, 01:54 AM   #4
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If you could blend the light coming off the LEDs and spread it evenly in the tank, optimizing would be a great option. Since we have cones of light to deal with, our limiting factors are physical space, heat sinking capability, and cost.

It seems to me that a 2:1 or 3:2 white/cool white to warm white is about as good as we average at present. Ask again next month, or next quarter and the emitters may be totally different.

On another hand, by the bag, Satistronics single 3 watt drivers are only $1.99 each so it' wouldn't be cost prohibitive to add red, blue, or UV spot lights to selected areas of a tank.
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Old 02-14-2011, 01:58 AM   #5
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Quote:
Originally Posted by Baadboy11 View Post
Either will grow plants just fine, it really boils down to which color do you like staring at and even that wont matter much once you get used to it. If you really want to get fancy you can always use both!
My plants had been doing okay under the strip of warm white LED's I'd been using until just recently. But there is of course always room for improvement.

And I certainly prefer the look of warm white over cool white, but I also want to supplement that to the benefit of my plants, but wasn't sure if plants prefer an equal amount of red and blue light or not.

This topic also begs the question though of whether we're limiting our plants by not providing the indigo/violet/ultraviolet light between 400 and 440 nm? (Actinic is about 420 nm).

However, this article http://www.americanaquariumproducts...._Lighting.html suggested that actinic light can cause algae in freshwater aquariums...

This thread looked helpful as well though. - http://www.plantedtank.net/forums/li...ts-absorb.html
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Old 02-14-2011, 02:08 AM   #6
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Quote:
Originally Posted by dbosman@msu.edu View Post
If you could blend the light coming off the LEDs and spread it evenly in the tank, optimizing would be a great option. Since we have cones of light to deal with, our limiting factors are physical space, heat sinking capability, and cost.

It seems to me that a 2:1 or 3:2 white/cool white to warm white is about as good as we average at present. Ask again next month, or next quarter and the emitters may be totally different.

On another hand, by the bag, Satistronics single 3 watt drivers are only $1.99 each so it' wouldn't be cost prohibitive to add red, blue, or UV spot lights to selected areas of a tank.
I'm testing these matters out on my current smaller trial tank as I plan out a large planted display tank. As such, I've been using inexpensive fleabay strips from China. They're low power, cheap, and easy to work with, so space, heat, and cost are not limiting factors certainly. And as the strips have a lot of individual diodes, spread is certainly not a problem. I'm using 1:1 warm white:cool white, which is looking okay to me.
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