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Thread: Algae and Kelvin Bulb Ratings, plus other light info

  1. #1

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    Algae and Kelvin Bulb Ratings, plus other light info

    Hey Guys I read through some of your light bulb suggestion and tests threads. Didn't want to derail the other threads, so here goes.....

    I am really surprised the consensus is that 2700K bulbs (CFL or perhaps general purpose LED) are better for algae growth than say 5100K bulbs!!!

    I have been using a 5100K 23W CFL flood for my refugium, based on this site: http://www.melevsreef.com/fuge_bulb.html
    where he tested the 5100K as being better for Chaetomorpha than 2700K. Was he mistaken somehow, or is macroalgae different than turf algae?

    My situation: I failed to get an ATS scrubber going for various reasons, but have a macroalgae/pod refugium under the tank. Going to switch from the CFL to an LED, probably PAR30 or PAR38 size bulb. I thought the circa 5000K was a given......but found the suggestions here. My refugium is growing red algae Halymenia, and green Halimeda fairly well. The more directional and powerful light of the LED should crank them up I suppose.

    Also looked into the LED grow lights, and sure enough, they are heavy on the red side. (Probably not at all good for my Halymenia). I am really surprised as I would somehow think that balanced daylight, equal red/blues (can lose the green of course), or else the noonday white 5000K (not the late day red shifted 2700K) would be better for Chlorophyll somehow. Anyone have an idea why heavy on the red would be better for green algae and plants?

    Which brings me to another conundrum - why so far on the blue side for the coral tanks? Is it really beneficial, or do we just like it because of the oceanic blue look plus the fluorescence it causes? Maybe the coral would actually grow faster under 2700K bulbs, or even red/purple plant grow lights?

    For the PAR38 type bulbs, I can get:
    2700K
    5500K
    etc.
    red/blue/purple grow light LEDs
    10,000K/Actinic Blue LED bulbs for coral tanks (see marinedepot.com).
    What is best for algae?

  2. #2
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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    The consensus seems to be that "warm white" bulbs work best.

    There is a thread here about a proposed experiment comparing different light sources

    viewtopic.php?f=2&t=1297


    I'm not sure if it's still ongoing though.

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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    all great questions,,I have always wondered the same thing,,maybe someone can help?

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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    Green algae absorbs more red light. We want green algae, so we use more red.

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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    OK -

    I seem to have answered my own question by trolling around. It turns out blue light uses more energy to produce (more watts) than red, yet each photon of either color produces the same amount of photosynthesis. So on an efficiency basis, you do better with red-shifted light. A moot point if you already are blasting lots of light, but for refugiums and ATS, efficiency is usually important.
    A good explanation here:
    http://www.reefcentral.com/forums/showt ... ?t=1496092

    Another way to look at this is that the photosynthetic action spectra you see usually show an equal red and blue peak, but if plotted on an energy basis, there is a higher red peak.

    I was a little worried about the narrow spectrum red+blue LED grow lights, especially for the red algae, which picks up more yellow-green to orange light due to phycobilins:
    http://www.emc.maricopa.edu/faculty/far ... ookps.html

    ... so went with the 2700K 14 Watt PAR 30 LED bulb (from the 5100K 23 Watt R40 CFL). Hopefully should work, although looking dimmer than the 5100K, it could have more PAR. The 5100K may be bright due to a relatively less useful spike in the green: http://en.wikipedia.org/wiki/File:Spect ... utions.png

    I'll see how this lamp does on the red Halymenia and the green Halimeda in there....

    Coincidentally, the guy at the fish store said that coral growers often use lower Kelvin light to get better growth, despite the fact that the rest of us use blue lighting for looks and to get more fluorescence. A bit counterintuitive given that undersea it's very blue shifted!

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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    It all comes down to the specific spectrum(s) the light puts off. Algae has a strong preference towards the chlorophyll A absorption peaks (420nm and 660nm) and corals have a strong preference towards the chlorophyll B absorption peak (strong 453nm and weak 620nm). So in a reef tank, more blue the better, up to a certain point, then you can have too much and cause death due to HEV (High Energy Visible Light) in corals which is super saturation of light in the blue spectrum. Algae on the other hand does not seem to utilize the chlorophyll B absorption peak much at all from my testing royal blue LEDs on algae, ie if you try to grow algae on a screen with LEDs, if you put one side all royal blues (450-455nm, which can grow corals well) and the other side 660nm far red LEDs (which can't grow corals at all), the side with the far red LEDs will flourish while the side with the blues will not grow at all. They do make 420nm LEDs now although they are hard to come by but that is my next experiment, to add some of those and see how it effects algae growth, one side all 420nm and the other side a 50/50 mix of 420/660.

    In terms of "kelvin", this translates to the lower kelvin usually having more of the red spectrum in the bulb, 2700k has the most red, 20k (or 20,000k) has mostly blue output. So for our needs, even on a refugium, 2700k is the standard bulb to buy because it is about the closest to outputting equal parts of reds and blues in an easy to find bulb, although most bulbs do not reach the far reds. If you want the absolute most efficiency, a 50/50 mix of just 2 spectrums, 420nm violet and 660nm far red light would be the best light to use for algae. Warm whites are good and very common to find and has more reds, so that is why it is the most widely recommended, but that doesn't mean it is the absolute best, but they are better than cool whites which have more blues but not violet.

    PAR (photosynthetic ACTIVE radiation) is meaningless for what 99% of people think it is used for, all PAR means is overall intensity of light between 400nm-700nm (pretty much the visible light spectrum), but it tells you nothing about the quality of the light (spectrum). Example I always throw out is you can have 100 PAR in 660nm light and have good algae growth or have 3000 PAR (the sun puts out 2000 PAR at noon on a clear day) in Blue or Green spectrum and have no algae growth at all, so that shows how PAR is not the end all be all for measurement. PUR (photosynthetic USABLE radiation, the wavelengths of light that the target can utilize) is the correct idea, but there really is no scientific data for PUR on specific corals or algae that I am aware of, which is what your link to the reef central article was pointing out. One reason blue is good on a display is depth, blue light having more energy penetrates the water much further so you can have corals deeper in the tank (Most lighting options do not come close to the output of the sun, so they need more blues to make up for it), and also corals do have a preference to the lower chlorophyll B absorption point as can be seen by the graph where as chlorophyll A is about equal in preference between the 2 spectrums.

    That doesn't mean other spectrums are not of value to us, they are very valuable actually, because the spectrums that are not absorbed by corals are reflected back to us which is the colors we see, other than the lower 400nm spectrum, which is different in that it excites florescent pigments within corals to give us the glow we love to see, so a wide range of spectrums is preferable in a display environment, but too much red, especially far reds, will promote more algae growth in a display. While it is true that a 6700k bulb does have a higher PAR output than any kelvin higher than it, 6700k is the least favorable kelvin to use in a display due to all the reds it emits. All spectrums will be absorbed to some degree by corals and plants, only some will be absorbed and utilized at a much higher rate so if you give them more of those specific wavelengths you will get better photosynthesis to a point, but too much of it can be worse than to little. This is where PUR comes in and all new sets of questions and experiments start running.


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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    Hmmm, Ace25 you are rather contradicting some of the other info.....

    In the RC thread, "greenbean" was definitely saying red is more watts efficient, hence better growth, than blues, pretty much regardless of taxa. Also saying that corals have a relatively flat spectrum in vivo, so you can discount the specific peaks you get on absorption for particular pigments. The conversion factor for watts into photons of the different wavelengths is a bigger effect.

    Like the Favia coral graph here: http://www.advancedaquarist.com/2002/2/aafeature

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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    Well we're getting somewhere on this issue it sounds like...

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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    That Advanced Aquarist article is great, and much more reliable than some RC post IMO.

    It is very true, as far as energy consumption is concerned, reds far outweigh blues due to the nature of light. Blue light requires about 2x as much energy to create a photon, but that energy is not wasted per se with blue because the extra energy that went into creating the blue photon gives it the "punch" power to penetrate water. 90% of 660nm red photons are simply filtered out within the first 3' of water, 50% within the first 12", which is the reason the ocean looks blue when you dive 10'+ under water, there are no red photons in the water anymore to reflect reds back at that depth. So you can put a red light above a tank with water in it and anything deeper than 12" will not receive much beneficial light. Corals have spent eons adapting to this fact, and utilize the blue spectrum much more efficiently because of the lack of red photons in the water. As far as a PAR meter goes, it just counts photons, it doesn't matter if they are blue, green, yellow, orange, or red, and all photons come out of a light source in equal amounts on a full spectrum light, it just takes 2x the power to create the blues. But we are not talking about energy to create photons here, we are talking about what Algae utilizes most efficiently in terms of specific spectrums. Some reason algae does not utilize 453nm spectrum to any measurable degree, where as corals utilize that spectrum to the extreme compared to the rest of the visible spectrum. I have not done testing yet with 420nm light, only 453nm on algae and corals, so I can not say "blue" does not grow algae, just that blue in the 453nm doesn't grow algae. 420nm may grow algae (and in theory should) just as well as 660nm light.

    This is really a simple experiment anyone can run themselves, and I have done it myself a few years ago, run all 660nm light above a 24" deep frag tank with test frags, and do the same on an identical size tank with only 453nm. Within a week, the side with only the red 660nm light over it will have almost 100% dead corals, if not dead, they will be severely faded and sickly and just about to die, where as the blue side will have white tips on the corals indicating growth (talking SPS/Acropora corals). This proves 2 things, 1. Red light does not penetrate much at all at 24" deep (PAR meter verifies this), and 2. the light that does penetration is not of sufficient spectrum or intensity to allow growth/photosynthesis and you will have bleaching, which is the exodus of zooxanthellae algae in the coral due to living conditions not being sufficient to support the algae in the coral any longer. Spectrum will ALWAYS beat intensity as far as which is the more important factor to lighting. Think of it like a shotgun to a sniper bullet. If you go by intensity alone, you use the shotgun approach, throw as much as the target and see what sticks.. while it will work, you waste a lot of energy with that method vs going by spectrum first, which is like a sniper bullet. One sniper bullet (spectrum) will do the same job as a shotgun shell with 1000 pellets but use far less metal to accomplish the same goal. You can run the experiment I mentioned above to prove that. Put a few 453nm Royal Blue LEDs over a frag tank (10-12 LEDs) and then put a 250w MH 10k bulb over another identical setup. Both will grow corals just fine, but one uses a narrow spectrum and uses a lot less power (10x3=30w vs 250w MH). This proves how spectrum trumps intensity in level of importance every time if your solely talking about photosynthesis, but intensity is a secondary concern and you have to meet a minimum requirement.

    Another way to look at it, you can put 4x the amount of Red LEDs over a tank to give 8x the PAR reading of a similar amount of blue LEDs, but even with 8x the PAR a few inches under the light, it still will not penetrate the water any further due to not having the energy stored in the photon to give it the punching power required to reach depths within water. I do like my corals to receive light it can use, and that means blues are the best option in a tank environment. If we are talking plants/open air where the resistance is not the same, sure, I can see how reds can work as well as blues because the reds do not get filtered out in air. There is a big difference when talking about the effects of density of the medium has on photons. I think a lot of people miss that part, they think of plants on land and how they react to light, but when you put something like water in between the light source and the target (coral/plant) then a whole new list of variables come into play.

    Here is a head scratcher to think about. Cree Royal Blue LEDs, a monochromatic light, using the same power supply and using the same amount of power according to a kill-a-watt meter puts out the SAME PAR as a Cree XP-G Cool white. Can anyone tell me why this is? If blue photons need 2x as much power to create, then the theory is Royal Blue LEDs drawing the same wattage should equal less PAR as a full spectrum LED like a Cree Cool White, but that is not the case, they are equal according to a PAR meter, where as neutral and warm whites are actually about 1/2 the PAR output of the Cool white and Royal blue LEDs, yet they consume the same power and have more reds in the output. I honestly do not know the answer to that and has been a head scratcher for me for a few years now because I don't know how to explain it, it goes against everything I have learned about how light works up to this point. Only two explanations I have heard that are plausible is 1. PAR meters can not accurately measure LED light so it is a flaw with the meter, but I can't say one way or the other if that has any truth to it or 2. Neutral/Warm whites are not mfg nearly as well as the cool whites and royal blues which gives them much less output overall.

  10. #10
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    Re: Algae and Kelvin Bulb Ratings, plus other light info

    Well that's an interesting point about the RB/CW/WW/NW PAR readings. one of my local reef club members has a PAR meter and told me that he felt that PAR meters were biased toward blue, but I can't recall why. When I ran that by the hydroponics lighting expert at lighthouse, he didn't agree. So I guess this is a completely worthless post but oh well...

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