Beyond LED Aesthetics-What spectra corals require

[Kolognekoral]

We have a great thread dealing with the aesthetic side of LED lighting. As that thread is to deal only with the visual optic, without clouding the issue with technical spectral requirements of corals and other reef inhabitants, here is a place where we can exchange notes on required spectrum and how to achieve it. I suspect we will have a great deal of cross-over from these threads. (fingers crossed)

Please feel free to post any infos read or personally collected concerning the well being or not of corals, etcetera under various LED fixtures and DIY projects. Here is the original Aesthetics thread

[scolley]

Thanks for starting this thread Jamie.

Determining if LEDs can provide our corals their photosynthetic needs is a HUGE issue that needs DEEP research.

Obviously this question has HUGE overlap with the presumably simpler question of "what LEDs make our corals look good?".

I hope the posters of both topics cross reference both login and links and inter-related information.

Thanks for starting this IMO critical thread...

Cheers.

[dots]

Yes, the spectrum and long term viability has been my concern with LED lighting in reefs......

[Belial]

I guess I will find out the hard way, picked up two 160watt LED units for a new 90 gallon I am trying to set up soon.
I want to run Acro, so as soon as I can the tank in the house and set up, will post results. Hopefully positive!

[jtma508]

I guess I'll repost some stuff from the aesthetics thread in case people here missed it. Here is an excellent paper on the subject http://www.int-res.com/articles/meps/117/m117p159.pdf. Read the 'Action spectra' section at the bottom of page 164 and Figure 8 on page 165.

Here is that work with the Cree XP-G whites, blue and royal blue overlayed (the grey line is the zooxanthellae requirements from the article cited):



As I've mentioned in the other thread, the zooxanthellae curve (in terms of its peaks) follows the spectra of the more popular MH and T5 (combos). In the LED realm it seems we're doing an OK job around the 450nm area but, as many people mention, could use some help in the violet/indigo area around 410nm. There are two obvious 'problems' with the LEDs. The first is in the ~480-500nm area (cyan) where the LEDs have a big trough. The second, though less dramatic, is in that ellusive ~680nm (deep red) area. The 'red' we do get from the white LEDs is in the orange-red area south of 625nm. This is increasingly true as we move toward cooler CCT's for the whites (CW being the weakest in the red range).

So, if we can risk censure by the thread nazis and briefly talk about aesthetics within this context, there is an obvious problem. We're blasting our tanks with blues which are seriously needed by our zooxanthellae buddies and make our tanks look good. But our white LEDs are providing a significant amount of green, yellow and orange which are not particularly needed by the zooxanthellae. But the aesthetic issue is evident. We have an over abundance of green and an over abundance of yellows. The yellows mix with our heavy dose of blue and give us what? Nope. You said green, huh? That would be true if we were dealing with paint but with light (additive mixing) we get white in the best case (equal amounts of R, G and B) or something dull and ugly in the worse case. You can play with this concept here: http://users.hal-pc.org/~clement/Sim...ng_Colors.html

This might explain the 'dull, washed-out' look some people complain about especially in regards to red specimens. What little red we're getting from the LEDs is being cancelled out by the ginormous amount of green and yellow. That's my theory. Meanwhile, in support of zooxanthellae, we're deficient in the cyan area and, again, that red around ~680nm.

[zygote2k]

Mr Brown said this:
" In order to make light a new wavelengths a phosphor (luminescent material) must be used, but are generally expensive and comes with drawbacks of their own. "

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.

[jtma508]

Probably because the LED industry is focused on general use (indoor and outdoor) lighting applications. They're not catering to the reefing community which represents a tiny market. LEDs are mass produced items. To interest the manufacturers there has to be very high market potential.

[Kolognekoral]

I would certainly agree, that reef aquariums are a fringe source of sales for LEDs, but this doesn't close out the possibility of specific types being produced in the near future. After all, we have many different T5 tubes available, which are designed specifically for various hobby lighting requirements. Yes, they are a bit expensive, but available.

At this point in time, I would think the fastest way to fill out the available spectrum would be with additional T5 lighting. This does have the immediate advantage of extending the blue range into the violet. The spectrum starting at 405nm is very inportant to corals.

While generally discussing spectrum, the article so kindly linked by jtma508 makes an assumption we may not need to make. It is dealing with the required, or better said utilized, spectra for zooxanthellae. The question for me is, just how important are the zooxanthellae for the well being of the coral? We now know that the corals are capable of covering their nutritional needs with considerably fewer zooxanthellae than most corals actually have. Indeed, corals will regulate their zooxanthellae populations via nutrient control, when in waters that are nutrient poor (< 0.01ppm PO4). In an aquarium, this low a level of nutrients is sought, but rarely maintained on a permanent basis. A reason why many aquarists have lightly browned corals. The corals are unable to control their internal nutrient level, as they would on a reef. In ULNS systems, such as zeolith/bacteria/carbon source systems, corals are clearly lighter in color and contain much lower densities of zooxanthellae. They are growing and otherwise healthy, which makes me wonder, just how important are the zooxanthellae? Clearly, they can be held a very low levels without stressing the corals.

This leads to the question, do we need to base our required lighting wavelengths on zooxanthellate needs or not? Is this why the red spectrum has not proved to be a problem with other lighting systems? Is this verging on infra red actually related to temperature reactions, as IR is actually noted as a heat source by the corals and perhaps the wavelength is not important, rather the heat it generates? As these higher wavelengths do not penetrate deeply into the water, perhaps it is the ambient heat of higher reef flats, warmed via the sun, that certain corals require, while others are perfectly happy at deeper than 10m with almost no red light and may even require these conditions. I am probably over simplifiing, but I suspect there is more going on here than directly meets the eye. We shouldn't assume that making the zooxanthellae happy means we are making our corals happy.

[jtma508]

Originally Posted by Kolognekoral

Is this why the red spectrum has not proved to be a problem with other lighting systems?

Well, Look at the spectra of popular MH and T5 bulbs. You'll see that ~680nm peak almost every time (well, of course not in a strictly actinic bulb). So my guess is the reason they don't 'struggle' with red is becuase they have the red in their spectra.

As for not worrying about zooxanthellae, if the hypothesis is that corals don't need zooxanthellae then we should be able to light an SPS tank the same way we do a FOWLR tank. There would be no photosynthetic requirement on the part of the corals and zoas. The fact is, there is a balance between the corals' internal food cycle and that provided by their zooxanthellae tenants. From the papers I've read, where we get into trouble is when we have deficient light (and spectra) and the zooxanthellae have to increase their numbers proportionately to make up for the lower light. Their increased numbers create that brown look we all know and love. I think what we need is to find that balance of water column nutrients and appropriate lighting (PUR) so the corals only hang onto the numbers of zooxanthellae they need without masking their colors.

[Kolognekoral]

Originally Posted by jtma508

Well, Look at the spectra of popular MH and T5 bulbs. You'll see that ~680nm peak almost every time (well, of course not in a strictly actinic bulb). So my guess is the reason they don't 'struggle' with red is becuase they have the red in their spectra.

As for not worrying about zooxanthellae, if the hypothesis is that corals don't need zooxanthellae then we should be able to light an SPS tank the same way we do a FOWLR tank. There would be no photosynthetic requirement on the part of the corals and zoas. The fact is, there is a balance between the corals' internal food cycle and that provided by their zooxanthellae tenants. From the papers I've read, where we get into trouble is when we have deficient light (and spectra) and the zooxanthellae have to increase their numbers proportionately to make up for the lower light. Their increased numbers create that brown look we all know and love. I think what we need is to find that balance of water column nutrients and appropriate lighting (PUR) so the corals only hang onto the numbers of zooxanthellae they need without masking their colors.

I think you misunderstood me. The red spectrum cannot be all important for corals (zooxanthellae?), as they do not necessarily receive it in large quantities in their natural habitat. In any case, has anyone located a red with a wavelength over 630nm? We would need 680nm to cover that peak. At 700nm it is only heat for our vision. Also, we tend to believe the the zooxanthellae are the main to only source of nutrition for corals. This has been proven to be quite untrue. That the zooxanthellae provide nutrients is clear, but the percentage and the level of dependance is not clear and seems to be very flexible. Literally all capture prey. Also, as we have two types of chlorophyll in play, which one is most important? Does this vary from coral to coral or from environment to environment. Each type has a different spectral preference it would seem.

As far as the brown being due to insufficient light, I have never been able to confirm this. I have found a stronger connection to available nutrients than to light. Not that one must rule out the other. I have corals that are almost white/pale grey with little light, while others under strong illumination are much browner than I would like. All in the same water, thus same nutrient load. We seem to be dealing with different types or abilities to adapt to variing conditions. I can't find a real rule of thumb.

Something I have noted in certain green corals is a change in pigment under lower nutrient conditions. They tend to turn pale blue. Why? Is this an adaptation to light? To nutrients? Both? Other green corals will turn brown under the same conditions and others will turn more yellow. Is this loss of control of the zooxanthellae population on the corals part ? Different chlorophyll preferences? Different zooxanthellae?

As we rarely know from what depth our corals were originally collected, it is hard to know what they were originally adapted to. Plus, propagated corals are another step away. Has their original colour and zooxanthellae density changed significantly under aquarium conditions? Most probably, don't you think?

There are an awful lot of unsatisfiing answers to many of these questions, IMO. We could certainly use some spectral readings under aquarium water of certain lighting systems that have proved successful. This may give us a better understanding of what the corals are actually getting. I am still using HQI and actinics, until I get a better understanding of what is required. The experiments are starting, but LEDs are considerably more expensive in Europe than in the USA ($8.00-9.00 each, optics around $4.00+). I don't want to throw money out the window. If the far red spectrum is unnecessary, then why add it. If under 450nm is not required, then we don't need to seek an ultraviolet. I do like this lower range for the fluorescence it brings, but this may be simple aesthetics.

[blasterman789]

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.

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.

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.

[Kolognekoral]

Originally Posted by blasterman789

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.

I think you might be being a bit too hard on the CW followers. (and i had thought the 'enough PAR' issue was well behind us, but maybe I am naive) I don't see this as being any different to the 10K people vs the 20K people. It really is aesthetics. I like a warmer note to the tank and refrain from the black light look, but that is me. Friends ask why my corals look different than those in the shops, but it is simply the lighting. Fashion, if you will. Neither here nor there, really.

Originally Posted by blasterman789

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.

I agree with you on this, the corals don't seem to require the far red spectrum at all, they are simply adapted to it in certain species/forms and may be able to utilize it, should it be available.That's like people eating certain foods as they are in season. Most of the info I've found concerning chlorophyll spectra is based on land plants and then translated to zooxanthellae. This simply gives a skewed picture as to the corals actual needs. And, as I mentioned previously, corals are predatory as well, they are capable of feeding themselves to a large degree. Their ability to regulate their metabolism is hardly researched and the various mechanisms are not understood. We have a great deal to learn, here, but we can still manage a good spectrum without understanding all of the mechanisms.

Originally Posted by blasterman789

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.

Absolutely, the 440-460nm range seems to be most suitable, but the question for me still remains, it the 440-450nm range crucial for the corals or not. Current Cree LEDs do not reach this range in real amounts (the NW does dip that low). If the zooxanthellae are not crucial to the corals well being, then this range may be unimportant for basic care of corals. Chlorophyll b is well served by the Cree LEDs.

Originally Posted by blasterman789

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.

OK, I have not found any hi-power LEDs between 400nm and 450nm. Can you give me a link? I would suspect that this range, as well as the range above 630nm is uninteresting for LED manufacturers, as the lower range is only needed for irradiating with UV, that is below the 400nm range and the higher range is simply largely heat and not conducive to LED longevity.

I wouldn't write off the 505nm to 550nm range just yet. This could be interesting, if not important. I just don't know one way or the opther. Do you have any specific references? or is this just personal aesthetic?

Originally Posted by blasterman789

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 going 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.

I suspect many of our corals come from about 10m depth and the red spectrum is not really present under 5m. I have a few wild colonies from much deeper and they certainly do not require red. I would suspect that only a handfull of collections have been adapted to tidal conditions. I think we generally agree on this, but others please chime in with opinions. Most HQI bulbs have little red in thier spectrum, but the lower K rating do have some. As to T5s, I don't use them and cannot really comment, plus, those spectral data I've seen do not seem to be representative, as spectrum in tubes changes rapidly with age and phosphor mix. Halides as well for that matter. I see LEDs as having a big advantage in the realm of spectral stability, but maybe this is not true. Data, can we trust it? Is it too early in this technology to be certain?

Thanks for the 10 rating! I suspect some interesting ideas will pop up on this thread, as well as the sister aesthetics thread.

[jtma508]

Originally Posted by Kolognekoral

I suspect many of our corals come from about 10m depth and the red spectrum is not really present under 5m.

Most HQI bulbs have little red in thier spectrum, but the lower K rating do have some. As to T5s, I don't use them and cannot really comment, plus, those spectral data I've seen do not seem to be representative, as spectrum in tubes changes rapidly with age and phosphor mix. Halides as well for that matter.

Reds penetrate to 15m (http://www.waterencyclopedia.com/La-...the-Ocean.html) and when you consider the DLI found in nature relative to our best setups (which provide less than half) this susumption may not be true.

On the second point, if you look at the spectra of either T5 or MH you'll consistently see the same spectral peaks.

[monkeydad]

Has anyone tried using red/green/blue LED combinations? If this combination works well creating colors, including white, on monitors, why not build an array of LEDs with this color combination?

Thanks,

[Kolognekoral]

Originally Posted by jtma508

Reds penetrate to 15m (http://www.waterencyclopedia.com/La-...the-Ocean.html) and when you consider the DLI found in nature relative to our best setups (which provide less than half) this susumption may not be true.

On the second point, if you look at the spectra of either T5 or MH you'll consistently see the same spectral peaks.

If you read the paragraph before that quoting 15m, you will see that 25% of all light is gone at 10m. For our eyes, the red spectrum is gone at 10 feet, which is about 3m. I was being generous with 5m. Yes, some long waves penetrate, but these waves are simply so quickly reduced, they really don't play a role anymore. Google some articles on underwater photography. You will get more of a feel of what is spectrally happening.

As to bulbs showing a spectrum with red peaks in their specs., my eyes cannot confirm this on comparisons with bulbs listed at the same spectrum. I really don't trust the reported spectrums. Certainly some are correct, but others are clearly not. Still, in my tank, which is 70cm deep, there is very little red left when the light hits the bottom in any case. Or I can't see it. Red corals placed at the bottom are no longer bright red in my tank. At about 12" from the HQI, they are red, 28" away and they are quite a bit 'browner', for lack of a better word. Some greens as well get much bluer, almost dark turquoise on the bottom, while yellows get greyish-green. Fluorescence or lack there of are playing a role, here.

Whatever is happening, I am convinced that the red spectrum is not playing a big role, except for the aesthetic side for some. As an artist, I consider myself very colour concious, which influences much of my perception. I guess we will have to wait and see, if the corals react differently over the years with less red under the LEDs.

[Kolognekoral]

Here is a link to an article I found very interesting. Much of the info has to do with light attenuation, but it gives one lots of thought material.

[Kolognekoral]

An interesting point on light penetration and colour optic, that we often forget, is the fact that an object under 20cm of water with a light source right above is showing NOT the amount of light filtered out at 20cm, but the light filtered out at 20cm PLUS the distance this object is from the viewing plane where the water ends. Therefore, we have distance from lightsource to object through water plus distance of object through water to the viewer. This partially explains why some of us see quite different colourations at similar depths. We fail to consider the additional distance through the water to the viewer, which can be considerable, even more than the first distance!

I doubt this has anything to do with the washed-out effect some people see, but this will play a factor in overall viewing. Yes, we had/have this with HQI and T5 lighting, however, we are tending to a multiple point lighting with LEDs, instead of a single point or overall source. This will influence our perception.

just some more thoughts.....