Lighting Wavelengths

[snaza]

Just wandering if there is a perfered wavelength for SPS. I'm using T5s and most bulbs have lots of 400-450nm. I understand Natural sunlight users 400-760nm but is there a percentage of each?

Just for argument sakes, just say i had 1000PAR, what wavelength would be best? 1000PAR at 400-450nm or 1000PAR of 500-600nm.

Does this make sense?

Aaron

 

[greenbean36191]

Just for argument sakes, just say i had 1000PAR, what wavelength would be best? 1000PAR at 400-450nm or 1000PAR of 500-600nm.

For all intents and purposes they would be equal. The 400-450 nm would be ever so slightly better in theory, but the differences wouldn't even be measurable.

Comparing watt per watt, you would do better with 500-600 nm since in practice you would get a higher PAR output per watt.

 

[snaza]

So it really comes down to PAR and not wavelength? What about LUX. Daylight lamps put out much more lux than blue lamps

 

[Diablo]

greenbean36191, your anwer would be correct if corals treated all light within the photosynthetically active range of ~400nm-760nm the same... but alas, they do not. Different "colors" are captured by the coral's photosynthetic pigments with differing efficiencies. Plotting capture-efficiency against wavelength, you end up with a coral's "Photosynthetic Action Spectrum". An example is given below:

Ever wondered why trees are green? Its because they absorb more red and blue and reflect more yellow-green, so the yellow green light gets to your eyes. Same goes for the zoxanthallae (algae) within the coral's tissue.

So looking at the chart, light in the 420nm to 470nm range is ~4x more effective than light in the 570nm to 630nm range. It is no accident that aquarium lights are skewed to the blue end of the spectrum.

As for Lux, it is a measurement of how bright a human will percieve the light to be, not how much light energy is present. Not a great measure for chosing aquarium lamps.

Its not important, but PAR is a classification of light, not a unit... micro-Einsteins (otherwise know as micro mole per second per meter square) is the unit to use.

 

[dots]

No, not exactly.....and I think I know where you going with this, so let me see if I can help you a little. (It looks like Diablo had the same idea and posted before me)

First things first......I can't remember the definition of Lux. Do you know why? Its a lighting industry term and not a good metric for aquarium lighting. PAR or PPFD (Photosynthetic Photon Flux Density) is the correct metric. I did this on purpose so as not to confuse myself. So forget you heard of anyone named Lux it won't be useful to you.

Wavelength refers to individual colors:

Violet - 400 to 440nm
Blue - 440 to 490nm
Green - 490 to 540nm
Yellow - 540 to 590nm
Orange - 600 to 650nm
Red - 650 to 700nm

Add all of these up and you get "visible" or "white" light.

Flourescent bulbs were found to be a little lacking in the "blue light' department. It was also discovered, corals did better with a little more blue light than these bulbs produced......so we "supplement" the daylight bulbs with some other bulbs in the "blue" range of 440 to 490nm.

So the daylight bulb is "all of the colors" but lacking in the blue department from what we need. Notice I said "all of the colors", but we don't talk about how much of each one. This is the kicker.........Each bulb from each manufacturer will "spike" at different places throughout ROYBIV.......this is what it "would come down to", which is the "spectrum" of light produced. Different spectrums have been found to stimulate different symbiotic algae clades and proteins within coral for growth and coloration.

At least for myself, I think of PAR as the "Quanity" of light.....and the Spectrum the "Quality" of light. But we don't know yet how much Quantity or Quality we need yet for "optimum" results.....so its a trial and error game still. (Which answers you original question)

As far as what is more important the "daylight" bulb or the "actinic" bulb in you tank? I would say the daylight because more of the PAR of the total lighting spectum is produced there as well as more wavelengths of light that make up this total spectrum.

I don't know if there are spectral plots for T5 yet, but for those of us who use MH, they are a valuable resourse in selection of bulbs.

I would suggest:

1.

Go to the FAQ's of this link and also be sure to read all the links on #10 of FAQ's
http://www.manhattanreefs.com/lighting

2.

Don't get caught up in chasing the perfect bulbs for growth and coloration quest. Lighting is only PART of the recipe for these two things. The Holy Trinity of: Flow, Water Quality, AND Light, is the key to the growth and coloration you are searching for. (Which is where I assume you are going with this)

 

[snaza]

Thanks guys that is awesome and exactly what i wanted. Is that example diablo, for coral in general or a specific coral? Im more interested in SPS here but yes i do understand water quality and flow are very important.

 

[snaza]

Is there a PAR level at which SPS stop absorbing light?

 

[greenbean36191]

Hopefully Chris will stop by soon since I don't have time this morning to give a full explanation, but yes, in practice, intensity is indeed much more important to photosynthesis than than spectrum, which is nearly irrelevant. Aquarium lights are blue because blue light produces more fluorescence, not because they're better for growth. In fact watt for watt, they're worse (because they have lower PAR/watt).

Yes, excessive PAR can be saturating or even damaging, but there is no set value where this occurs. It will vary from coral to coral.

 

[snaza]

on the graph there is a big peak around 650-700. Not many bulbs cover that wavelength

 

[greenbean36191]

Ok, got a bit of a break, so time for the book-

First some simple explanations of what PAR and action spectra mean.

PAR is a count of photons within the 400-700 nm range hitting a surface per unit of time. It makes no distinction about what color those photons represent. Photons of all colors count equally.

Action spectra are a measure of what percentage of those photons are captured at certain wavelengths. They don't tell you how efficiently light of specific wavelength is used for photosynthesis.

The spectrum above has a fairly normal general shape for zooxanthellae, in that there is a peak in the blue, trough in the green and yellow, and another slightly smaller peak in the red. However, the blue peak is usually much broader and the yellow/green trough is much less pronounced. Usually it's at least half of the blue/cyan peak. If Chl a and peridinin are the only pigments included in the spectrum then that may explain why it looks like that. There are half a dozen pigments that make up the complete spectrum for zoox though. The exact spectrum will change over time too.

The important thing though is that corals absorb well across almost all of the PAR spectrum. Even at their worst bands they still typically absorb ~40% or more. Corals catch most of the light that hits them, regardless of what color it is. Because of that, the action spectrum really only becomes important when you're talking about PAR well below saturation. Otherwise you're still taking large percentages of very large numbers (like 10^20). As PAR increases, the spectrum becomes less and less relevant. Reef tanks (especially "SPS" tanks) tend to have fairly high PAR, like with the example of 1000 umol/m^2/s.

Because of the way photochemistry works, all photons in the PAR spectrum are equally useful for photosynthesis. You don't get any more work from an energetic blue photon than from a lower energy red one. In fact, blue light is utilized less efficiently, in that the extra energy as compared to a red photon is lost in the form of heat of fluorescence. The coral might be 2x more likely to catch that blue photon, but then something like 75% of its energy is wasted once it's captured. The thing is, you spent your wattage trying to put that energy into the photons to begin with. Since blue photons are more energetic than red, you get fewer of them (less PAR) per watt of power input. Fewer photons means less photochemical work and less production. Assuming the OP is not going to upgrade the wattage of his lights to make up for the lower PAR, the corals would benefit more from a higher K spectrum.

 

[fijiblue]

Ok, got a bit of a break, so time for the book- First some simple explanations of what PAR and action spectra mean. PAR is a count of photons within the 400-700 nm range hitting a surface per unit of time. It makes no distinction about what color those photons represent. Photons of all colors count equally. Action spectra are a measure of what percentage of those photons are captured at certain wavelengths. They don't tell you how efficiently light of specific wavelength is used for photosynthesis. The spectrum above has a fairly normal general shape for zooxanthellae, in that there is a peak in the blue, trough in the green and yellow, and another slightly smaller peak in the red. However, the blue peak is usually much broader and the yellow/green trough is much less pronounced. Usually it's at least half of the blue/cyan peak. If Chl a and peridinin are the only pigments included in the spectrum then that may explain why it looks like that. There are half a dozen pigments that make up the complete spectrum for zoox though. The exact spectrum will change over time too. The important thing though is that corals absorb well across almost all of the PAR spectrum. Even at their worst bands they still typically absorb ~40% or more. Corals catch most of the light that hits them, regardless of what color it is. Because of that, the action spectrum really only becomes important when you're talking about PAR well below saturation. Otherwise you're still taking large percentages of very large numbers (like 10^20). As PAR increases, the spectrum becomes less and less relevant. Reef tanks (especially "SPS" tanks) tend to have fairly high PAR, like with the example of 1000 umol/m^2/s. Because of the way photochemistry works, all photons in the PAR spectrum are equally useful for photosynthesis. You don't get any more work from an energetic blue photon than from a lower energy red one. In fact, blue light is utilized less efficiently, in that the extra energy as compared to a red photon is lost in the form of heat of fluorescence. The coral might be 2x more likely to catch that blue photon, but then something like 75% of its energy is wasted once it's captured. The thing is, you spent your wattage trying to put that energy into the photons to begin with. Since blue photons are more energetic than red, you get fewer of them (less PAR) per watt of power input. Fewer photons means less photochemical work and less production. Assuming the OP is not going to upgrade the wattage of his lights to make up for the lower PAR, the corals would benefit more from a higher K spectrum.

What is your resource for this? Your statement that the corals would benefit from a higher K spectrum contradicts what was stated above...

 

[snaza]

Thanks a lot greenbean, that really helped me out. Is there somewhere that lists corals PAR saturation?

Fiji - Your tank is still one of my favorite T5 Tanks. Any updates anywhere. I know your tek puts out heaps of PAR.

cheers

Aaron

 

[greenbean36191]

What is your resource for this?

A lot off it would be considered "common knowledge." The rest comes from the work of dozens of authors on the subject- Dubinsky, Hoegh-Guldberg, Fricke, Titylanov, Shick, Fitt, etc.

Your statement that the corals would benefit from a higher K spectrum contradicts what was stated above.

That's because it was a typo. The corals would benefit more from a lower K spectrum because of the higher PAR.

 

[greenbean36191]

Is there somewhere that lists corals PAR saturation?

No, because this information would be essentially useless. Saturation intensities vary from coral to coral based on environmental conditions. They are not consistent for a single species or even a single individual over time. A coral from the reef crest might take 2500 uE/m^/s to be saturated whereas a close relative can be saturated at 10 uE much deeper on the reef.

Based on my own measurements on the reef guesstimate would be in the range for 500-2500 uE which represents the noontime PAR values from 5-70 feet in the Red Sea.

 

[Zimster]

Why is it advised to have 60% blue and 40% white light then if all light over the spectrum is going to have the same effectiveness then?

Here's my thoughts:
If blue light (say 460nm) is incident on a coral with a 54 watt T-5 bulb, it will be used twice as efficiently as light in the yellow-green part of the spectrum. If white light gives off more photons than blue light because of the given max power (54 watts), then one would think that the white light would give more energy to the coral than the blue light, when in fact the blue light gives the same amount of energy (given by the equation E=hf where E is the energy of a photon, h is 6.626068*10^-34, and f is the frequency of the light {1/wavelength}) as the white light does with less photons. If this is true then blue light (~14000K-20000k {440nm-520nm}) will be much more effective to the coral in producing more food/energy for the coral. In turn i believe that blue light is much more crucial to keeping corals than white light is and the question that i have seems to be yes. I am wondering what you think about this.

On the other hand, when talking about the black body spectrum, the sun's intensity temperature is about 5900K. According to the graph below, the sun is most intense in the blue, green, and yellow region. When the sun hits the ocean, most colors of light get reflected, causing glare, but blue penetrates very nicely and much deeper than all other wavelengths. The other wavelengths that get through, dissipate very fast because of rayleigh scattering from the particles of H2O and various others. Blue light has the strongest intensity in the water of all wavelengths. When white light enters your tank water, alot of it will get reflected and the usable part of that to the corals will be even less. When you start out with blue light, more energy gets delivered to the coral with out as much loss. Therefore, this is why i believe it is better to have higher temperature values of K (~14000K-~20000K {440nm-520nm}) on your tank when it comes to the coral.

 

[fijiblue]

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Is there somewhere that lists corals PAR saturation?
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Yes there is, but it is still somewhat generalized:
http://www.advancedaquarist.com/2007/3/aafeature1/view?searchterm=too much light


green bean - Do you have a specific link to a journal? I would hardly consider this topic "common knowledge" since it is probably the number one most talked about, unknown subject on here - especially considering a thread was started asking about it

snaza - Thanks for the compliment. A sad update is I switched over to MH's to compare results. I treat my tank like a science experiment...always testing. I tried T5's for a year and now will try MH on the same system. So far, T5's smoke the MH on my system. It seems easy to hit the high PAR numbers with the T5 blue bulbs, so I would recommend more blue and less daylight for good results.
On a side note, I will be updating the T5 energies thread soon with a new finding from Dana Riddle!

 

[greenbean36191]

Much of the info is common knowledge in that it's not discussed in journal articles because it's assumed that the authors and audience are already familiar the definitions and significance of things like PAR, activation spectrum, and how photosynthesis works. Whether this is common knowledge to hobbyists is a different matter.

What specifically do you want a journal citation for? My long post was a synthesis of the work from several dozen papers. Unfortunately, people don't write papers specifically answering which bulb combination is ideal. If there are specific points you want to read more about I can probably help. Otherwise it's a pretty vague request.

 

[greenbean36191]

Why is it advised to have 60% blue and 40% white light then if all light over the spectrum is going to have the same effectiveness then?

Redder light provides better growth, but doesn't promote fluorescence. Bluer light isn't quite as good for growth, but most people find it more aesthetically pleasing. There's nothing scientific about the ratio. It's just a compromise between growth and looks.

If blue light (say 460nm) is incident on a coral with a 54 watt T-5 bulb, it will be used twice as efficiently as light in the yellow-green part of the spectrum. If white light gives off more photons than blue light because of the given max power (54 watts), then one would think that the white light would give more energy to the coral than the blue light, when in fact the blue light gives the same amount of energy (given by the equation E=hf where E is the energy of a photon, h is 6.626068*10^-34, and f is the frequency of the light {1/wavelength}) as the white light does with less photons. If this is true then blue light (~14000K-20000k {440nm-520nm}) will be much more effective to the coral in producing more food/energy for the coral. In turn i believe that blue light is much more crucial to keeping corals than white light is and the question that i have seems to be yes. I am wondering what you think about this.

Photosynthesis doesn't work this way. A blue photon is exactly equal in its ability to produce sugar as a red one. The excess energy in the blue photon is lost as heat or fluorescence until the energy is equal to that of a red photon. Despite the extra energy of the blue photon it's no more useful to the coral than a red one once it's collected. 1 red photon produces exactly as much food for the coral as 1 blue one.

As for attenuation, I'll let you crunch the numbers on that one. We're talking about depths of 2, maybe 3 feet. I haven't done any testing, but I suspect you'll find that attenuation doesn't make up for the initial PAR disparity.

 

[Zimster]

awesome! thanks....i never knew that any photon at any wavelength is able to produce the same amount of sugar....

i have a bunch of SPS corals and i have studied much about lighting systems.....currently i have a 6 bulb T-5 lighting system with 50% 10000K and 50% 460nm. I was planning on getting another blue bulb between 420 and 500nm (to replace a 10000K).....in your opinion....would you recommend getting a 6700K also?? Thanks

 

[fijiblue]

Whether this is common knowledge to hobbyists is a different matter.

Well, considering we are in a hobbyist forum...

You don't get any more work from an energetic blue photon than from a lower energy red one. In fact, blue light is utilized less efficiently, in that the extra energy as compared to a red photon is lost in the form of heat of fluorescence. The coral might be 2x more likely to catch that blue photon, but then something like 75% of its energy is wasted once it's captured.

In particular, this if you don't mind.