# Best color in LED lighting?



## StrangeDejavu (Jun 23, 2014)

While looking up certain brand of LED lighting for a shrimp tank on YouTube, I came across a comment from a user that got me thinking. Is he talking out of his butt or is there some truth to this?



> Just to give you a heads up....Optimal plant growth is achieved within the violet spectrum. The white lights should be full spectrum; are primarily for human and animal sight. The plants do benefit from it also, but if you have just red and blue lighting they'de grow great. Japan has been researching on this for years to grow food. I purchased this same light and added extra blue and red lights...the plants are growing like gangbusters.


I use the Satellite+ LED unit on my 55g, and I usually use the violet 6500k button as it offers the most color-correct version of the tank to my eyes. Should I instead be using blue or red?


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## Solcielo lawrencia (Dec 30, 2013)

Chlorophyll A+B primarily uses blue+red spectrum. That's why plants are green, because these pigments absorb the blue+red spectrum and reflect the green light, which, for the most part, aren't useable.

If you only had green light, the plants will die unless the intensity of that green is so strong that it makes up for the lack of useable light energy.


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## StrangeDejavu (Jun 23, 2014)

Solcielo lawrencia said:


> Chlorophyll A+B primarily uses blue+red spectrum. That's why plants are green, because these pigments absorb the blue+red spectrum and reflect the green light, which, for the most part, aren't useable.
> 
> If you only had green light, the plants will die unless the intensity of that green is so strong that it makes up for the lack of useable light energy.


So which color combo from my unit would offer the best growth for my plants? I can choose between:


6500K/Orange
6500K/Blue
6500K/Rose Pink
6500K White
Full Spectrum
6500K/Purple
I'm currently using Rose Pink, but should I switch to Full Spectrum or Blue instead? Still new to this so i'm kinda learning as I go.


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## Solcielo lawrencia (Dec 30, 2013)

You'd have to look at the actual radiometric outputs of the LEDs and find the one that matches the chlorophyll absorption spectra best.


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## klibs (May 1, 2014)

Solcielo lawrencia said:


> You'd have to look at the actual radiometric outputs of the LEDs and find the one that matches the chlorophyll absorption spectra best.


+1

The temperature in K is really just how our eyes see the light (I think - someone correct me if I'm wrong). This image is a good reference point:


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## StrangeDejavu (Jun 23, 2014)

Thanks guys, I did a little searching but came up with nothing. Based on the above graph, my best bet is to continue using the violet LEDs.


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## jeffkrol (Jun 5, 2013)

StrangeDejavu said:


> Thanks guys, I did a little searching but came up with nothing. Based on the above graph, my best bet is to continue using the violet LEDs.


your under a misconception.. Sat plus has no "true" violet.. all it has is this in graphic form:









And this:









All "colors" besides white are derived from the RGB LED's in various intensities..

Full spectrum (all on) is the most PAR..
Regardless of the inaccuracies of the PAR meters..

Adjust the RGB to "taste"..by dimming the least effective.. green..
After that adj. r/b to refine the color to your liking..

Actually your "violet" color does just that.. dims the green........


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## Solcielo lawrencia (Dec 30, 2013)

klibs said:


> +1
> 
> The temperature in K is really just how our eyes see the light (I think - someone correct me if I'm wrong). This image is a good reference point:


Yeah, the Kelvin is just how our human eyes perceive the color. It doesn't tell us very much about the useful radiation that plants use. 

Also, that absorption spectra is for chlorophyll A only, which reaches a peak at ~430nm and ~660nm. Chlorophyll B's peak absorption is ~450nm and ~640nm. Both the blue and red wavelengths are important for growth.

http://www.biologie.uni-hamburg.de/b-online/e24/3.htm

Blue tends to cause plants to have very short internodes. Red causes plants to have long internodes. There are many other variables that red-blue light controls including leaf size.


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## StrangeDejavu (Jun 23, 2014)

jeffkrol said:


> your under a misconception.. Sat plus has no "true" violet.. all it has is this in graphic form:
> 
> 
> 
> ...


Very informative, thanks. :thumbsup: Bummer that i'll have to use a custom setting as the Satellite Ramp Timer only works with the default values. Apparently custom settings + Ramp Timer = strobe light for those 15 minutes. I'm more concerned about happy plants, however, so i'll have to figure something out regarding the timer.


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## klibs (May 1, 2014)

FYI for any bulbs / fixtures you buy you should be able to find a spectrum output graph like the ones provided in this thread. Easy way to see if the light will work for you.

Thanks for the clarification Solcielo! I just quickly googled that graph lol


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## StrangeDejavu (Jun 23, 2014)

While feeding the fish, I messed with the fixture some. I turned on Full Spectrum and completely removed green. When I looked at the LEDs, the non-white ones were the same violet color the other preset shows. Next, I clicked on the violet preset and absolutely nothing changed so I guess I was always using the best lighting option without knowing.  I think I eventually may replace the fixture as it's running at 0.5 WPG with a PAR of about 21... very, very low light, lol.


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## mattinmd (Aug 16, 2014)

It should also be noted that plants do use a much broader spectrum for photosynthesis than the chlorophyll A + chlorophyll B spectrums suggest.

There are other pigments, such as carotenoids, that also absorb energy and feed photosynthesis, but are much less efficient.

A little bit of searching for "photosynthetic action spectrum" or "photosynthetic response spectrum" will show a few graphs for these. 

There are also several versions of these graphs around, with different depths of "dip" at the green spectrum.

I suspect (but cannot confirm with fact) that the differences are based on studying the response of different plants, some of which may have different balances of chlorophyll vs other pigments. I would expect this curve to be different for red-leaf low-light land plants (ie: red coleus) vs all green plants (ie: grass or lettuce), and I expect there is similar variation among aquatic plants.


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## Regelian (Sep 14, 2014)

klibs said:


> +1
> 
> The temperature in K is really just how our eyes see the light (I think - someone correct me if I'm wrong). This image is a good reference point:


Thanks for posting the grafik. As mentioned, only one of the chlorophylls is noted. 

Yes, kelvin is nothing more than colour. It has nothing to do with the spectrum involved in creating the colour. With LEDs the reference is literally useless and should be avoided in selecting LEDs for a lighting array. We need to know the actual wavelegths involved and the intensity of the LED.

When creating a basic array of LEDs you should use 405nm (violet), 420nm (indigo for a name), 450 (royal blue), 470nm (blue), 620nm (red), 660nm (deep red) and maybe neutral or cool white to aid in toning for the human eye. I stay away from warm white as it tends to promote nuisance alge and cyanobacteria, which can collect radiations in the yellow to orange range.

cheeers,


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## jeffkrol (Jun 5, 2013)

Regelian said:


> Thanks for posting the grafik. As mentioned, only one of the chlorophylls is noted.
> 
> Yes, kelvin is nothing more than colour. It has nothing to do with the spectrum involved in creating the colour. With LEDs the reference is literally useless and should be avoided in selecting LEDs for a lighting array. We need to know the actual wavelegths involved and the intensity of the LED.
> 
> ...


We could argue all day re: the "necessity" of violet and possibly indigo.
Though I feel they certainly do no harm.they tend to be an unnecesary and a relatively costly addition..









http://5e.plantphys.net/article.php?ch=t&id=66

Effectiveness is already trailing off at  450nm.. Much depends on who and how one did the measurements..

IF you have some current proof of the need for this wavelength for fw plants I'd appreciate it...











Plenty is "absorbed" but underutilized from about 435 on down:









http://plantsinaction.science.uq.ed...-absorption-and-photosynthetic-action-spectra











> Although UV wavelengths are absorbed by leaves and would be capable of driving photosynthesis, such short wavelengths are damaging to biological systems and plants have adapted by developing a chemical sunscreen. Consequently, the quantum yield from these wavelengths drops off markedly below about 425 nm.











http://biology.mcgill.ca/Phytotron/LightWkshp1994/1.5 Bugbee/Bugbee text.htm

http://forums.gardenweb.com/forums/load/lights/msg0202134830483.html?31









General consensus seems to be you lose "efficiency" after 435nm........ though certainly useable.. Critical? not so much.
This "field" is open to correction of course....









One more:








https://www.icmag.com/ic/showthread.php?t=200834&page=4


> In the three graphs (above) one can see three different methods of measuring light: that which leafs absorb (1st graph); incident photons relative to photosynthesis (2nd graph); and quantum yield of wavelengths from K.McCree's work, i.e., his ASP. We should use graph C, from K.McCree's ASP when judging the SPD of lamp in terms of the lamp's ability to drive photosynthesis:


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## aja31 (May 25, 2013)

Great explanation Jeffkrol!

Also remember that most of these studies (if not all) have been done for terrestrial plants. There are additional factors that might effect aquatic plants that we use.

Most notably 660nm light experiences ~10% absorption by water after 25cm of travel. For shallow tanks not a concern, but for larger and deeper tanks it could be a consideration. Also it may be that aquatic plants have evolved to use red light less efficiently due to this attenuation of redder light, depending on the depth these plants are naturally found at. These are of course unknowns since there hasn't been much research on the subject that I could find for aquatic plants. So it may be that for us red lights are also not as efficient as the chl a+ b graphs would lead you to believe.


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## jeffkrol (Jun 5, 2013)

aja31 said:


> Great explanation Jeffkrol!
> 
> Also remember that most of these studies (if not all) have been done for terrestrial plants. There are additional factors that might effect aquatic plants that we use.
> 
> Most notably 660nm light experiences ~10% absorption by water after 25cm of travel. For shallow tanks not a concern, but for larger and deeper tanks it could be a consideration. Also it may be that aquatic plants have evolved to use red light less efficiently due to this attenuation of redder light, depending on the depth these plants are naturally found at. These are of course unknowns since there hasn't been much research on the subject that I could find for aquatic plants. So it may be that for us red lights are also not as efficient as the chl a+ b graphs would lead you to believe.


Yep.. and a lot has been done on algae (boo) and *zooxanthellae* ( endosymbiotic dinoflagellates,unicellular algal protists in coral)
(mouthful)

Each w/ subtle and not so subtle differences I suspect.. As for depth penetration.. well royal blue is no more or less effective at "normal" tanks as any violet/indigo..

I'd put more bets on "red"..  Most aquarium plants are also "emergent" plants.. very used to terrestrial light. 











> PAR as described above does not distinguish between different wavelengths between 400 and 700 nm, and assumes that wavelengths outside this range have zero photosynthetic action. If the exact spectrum of the light is known, the photosynthetic photon flux density (PPFD) values in μmol/s can be modified by applying different weighting factor to different wavelengths. This results in a quantity called the yield photon flux (YPF).[1] The red curve in the graph shows that photons around 610 nm (orange-red) have the highest amount of photosynthesis per photon. However, because short-wavelengths photons carry more energy per photon, the maximum amount of photosynthesis per incident unit of energy is at a longer wavelength, around 650 nm (deep red).



10% loss on a wavelength that could be considered 20-50% more "efficient????

for fun:
http://www.advancedaquarist.com/2013/12/lighting


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