# Spectrum...doesn't matter...does it?



## Tim Harrison

I've been reading on this forum for some time now that spectrum doesn't matter. I'm not entirely sure what this means.

I can't be the only one who is struggling with this so I think it would be a great help if we could pin it down to a precise explanation.


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## BigTom

I'm pretty sure there's a thesis by Clive on the matter in one of the other threads if you have a good look.


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## ltsai

Yeah. I think Clive mentioned that the plants don't care what type of light, as long it is visible to the naked eye. Kelvin doesn't matter.  

Question for Clive:
Does it matter if it's marine actinic light or Arowana tanning light??


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## NattyAntlers

Think this covers actinic light.
actinic lighting vs algae growth | UK Aquatic Plant Society


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## Tim Harrison

Thanks guys...of course I value Clive's knowledge and opinion but I also value that of others too, so if you have any thoughts I'd love to hear them...Then maybe we can get some sort of discussion going - which is something this forum does particularly well.


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## bridgey_c

I think you might have to be more precise about what it is you don't understand about the previous discussions. Or what it is you don't agree with and why. I hope that doesn't sound abrupt but put some meat on the bone, lol


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## Henry

I think the theory that certain kelvin ratings cause problems in planted tanks is so deep seated among aquarists, it's difficult to accept otherwise. To take the word of one man over thousands of others saying the opposite is not an easy thing to do, especially when you believed the thousands in the past.

I prefer a warmer light in my tanks, and so avoid actinics like the plague anyway.


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## BIN578

Id it doesn't matter, why have manufacturers like TMC made such a think about making their growbeam range specifically at the 6500K range ?  Why would they not just make LED's at a range of temperature levels if its purely an aesthetic thing ?


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## George Farmer

I'm one of those people that claim that plants aren't fussy about spectrums.

Sorry, I can't prove it through experimental data, but I can say I've probably tried over 50 types of lighting over the years with varying spectrums and can't say one is better than the other. This is why my lighting choice is now purely based on aesthetics (colour rendition as well as the unit design) and cost (initial purchase and running cost).

It wouldn't surprise me if plants readily adapt the whatever spectrum is present. I think most plants we grow are aquatic weeds that are very opportunistic and able to utilise what's available. This principle also applies to nutrient levels, as we know.



BIN578 said:


> IWhy would they not just make LED's at a range of temperature levels if its purely an aesthetic thing ?


They do. The Colour-Plus tile is now marketed under the GroBeam range because TMC realise it grows plants very well too, as does the marine 1500XG tile (9000K).


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## ceg4048

Troi said:


> I've been reading on this forum for some time now that spectrum doesn't matter. I'm not entirely sure what this means.
> 
> I can't be the only one who is struggling with this so I think it would be a great help if we could pin it down to a precise explanation.


Hey Troi,
			I believe this is a cleverly constructed trick question specifically designed to see who's been paying attention.

However, I have solved the riddle:
You have in fact, NOT been reading that spectrum doesn't matter, or that there are no effects of spectrum. What you've reading is that spectrum has negligible effects on plant growth rate and overall health.

There are a multitude of effects of spectrum, but those effects have little to do with whether you should worry about or be restricted to only using a specific color for the sake of the health of your plants.

In any case, there is plenty of talking about spectrum ad nauseum, but I notice that there are very little actual doing. You can answer this question yourself by simply using a specific color bulb on newly bought plants and record their growth with images, say for 8 weeks. Then repeat using a different color bulb. You can even go as far as to weigh the plants at the beginning and at the end of the test period to record the mass increase. Pick an easy plant, and purchase each batch from the same vendor to eliminate effects of inconsistent quality. Then repeat using a different plant. Note the results.

What you'll discover is that the thousands of people who say there is an effect on growth and health are all say this because they saw where someone else said it. The few people who say there is NO effect on growth and health are people who actually have tried it.

As far as any other effects of spectrum, well the effects can be very interesting, but not vital.
Example of a spectrum effect I quote from another post:


> It turns out that as light enters water, different wavelengths with different "energies" will penetrate to varying depths. Red light (630-780 nanometers) penetrates only to about 15 meters, while blue light (420-490 nanometers) can penetrate to as deep as about 250 meters. This is why the ocean appears blue.
> 
> Actinic bulbs peak somewhere in the 420 nm range. Any plant can use blue light, not just algae. In general, red light stimulates photosynthetic carbon fixation which is incorporated into glucose, while adding blue light causes a metabolic shift so that the fixed carbon is used to synthesize organic acids, amino acids and proteins. As long as the intensity (i.e Photon Flux Density) of the light is sufficient to fix carbon from ambient CO2 the wavelength within the spectrum is irrelevant.


 
To give context to the quote, that was taken from a thread where someone assumed that blue light causes algae.

The other thing I wanted to mention is that I'll be willing to bet that LFS and online shops sell more so called "ideal color" bulbs (6500K) than any other color. And, I'm willing to bet that because of Matrix programming, most plant growing pre-programmed zombi hobbyist are using 6500K bulbs (because they were told to do so by thousands of other zombies), and yet, whenever a problem thread is posted on any of The Matrix websites, the zomby usually reports that they are presently using 6500K bulbs.

Now, of course it would be totally unfair, and totally inaccurate to blame their 6500K bulbs for their abysmal failure, but my point would be that 6500K did not save their plants from descending into total oblivion. From that I would conclude that a hobbyist is just as likely to have plant problems and algae using 6500K bulbs as he would using any other color bulb. That alone could be used as an argument that indeed, spectrum does not matter.

It's entirely possible that spectrum has an effect in terms of pigment production, and changes in pigment production in the leaf can have an effect on the color of the leaf, so if enough testing is done you might be able to arrive at a color combination that turns certain plants to the color you find most pleasing. A more detailed response on effects in actinic lighting vs algae growth | UK Aquatic Plant Society

So my message to thousands of test kit lovers is to stop testing kits and start testing the validity of Matrix propaganda.

Cheers,


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## Henry

The title of your book should be "Marxist Aquatics".


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## BIN578

George Farmer said:


> I'm one of those people that claim that plants aren't fussy about spectrums.
> 
> Sorry, I can't prove it through experimental data, but I can say I've probably tried over 50 types of lighting over the years with varying spectrums and can't say one is better than the other. This is why my lighting choice is now purely based on aesthetics (colour rendition as well as the unit design) and cost (initial purchase and running cost).
> 
> It wouldn't surprise me if plants readily adapt the whatever spectrum is present. I think most plants we grow are aquatic weeds that are very opportunistic and able to utilise what's available. This principle also applies to nutrient levels, as we know.
> 
> 
> They do. The Colour-Plus tile is now marketed under the GroBeam range because TMC realise it grows plants very well too, as does the marine 1500XG tile (9000K).


 
Thats interesting.  So (with no expense spared) something like the Ecotech Radion unit, which from what I read you can change the colour ad nauseum) would be ideal for someone who cares more about lighting appearance ?  I have to admit to liking the idea of having different colours, not only to make the plants look their best, but sometimes to make the fish look their best too... a bit like butchers who used to use redder lights to make their meat look fresher, LOL.


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## George Farmer

BIN578 said:


> Thats interesting.  So (with no expense spared) something like the Ecotech Radion unit, which from what I read you can change the colour ad nauseum) would be ideal for someone who cares more about lighting appearance ?  I have to admit to liking the idea of having different colours, not only to make the plants look their best, but sometimes to make the fish look their best too... a bit like butchers who used to use redder lights to make their meat look fresher, LOL.


Exactly, but... I've used the Radion and found the glitter lines too distracting due to the intense point source effect. It's marine-bias with more blue/royal blue LEDs too which most planted aquascapers wouldn't use so much.


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## ceg4048

Henry said:


> The title of your book should be "Marxist Aquatics".


No that one's already taken and is currently being taught at universities throughout The Matrix.

I was thinking more of "Groucho Marxist".

Cheers,


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## BIN578

George Farmer said:


> Exactly, but... I've used the Radion and found the glitter lines too distracting due to the intense point source effect. It's marine-bias with more blue/royal blue LEDs too which most planted aquascapers wouldn't use so much.


 
So which do you think is the most flexible and aesthetically pleasing that provide the advanced functions of LED controllers ?  If only TMC would make their colourplus so that the colours could be individually controlled, it would be much better accepted, especially as its at quite a good price point  as it currently stands.  I saw one sell second hand for £50 on ebay a couple of weeks back.  I very nearly bought it myself but was not sure if it would look nice in the tank.


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## Tim Harrison

ceg4048 said:


> You can answer this question yourself by simply using a specific color bulb on newly bought plants and record their growth with images, say for 8 weeks. Then repeat using a different color bulb. You can even go as far as to weigh the plants at the beginning and at the end of the test period to record the mass increase. Pick an easy plant, and purchase each batch from the same vendor to eliminate effects of inconsistent quality. Then repeat using a different plant. Note the results.


 
I think that this has been done here...http://www.apms.org/japm/vol15/v15p29.pdf ...

...Effects of Light Quality on Growth and Chlorophyll Composition in Hydrilla (T.K. Van et al)

It perhaps shows things in a different light


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## Ian Holdich

I'm also in the same camp as George. I haven't got the means to stringent scientific testing, however anecdotal evidence in this hobby goes along way (as long you know what you're doing). I have used different spectrum bulbs and there hasn't really been a different in plant growth or formations in the leaves. Again, aquatic plants are opportunistic weeds, that have the ability to adapt to different situations. It's survival of the fittest.


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## Tim Harrison

Ian Holdich said:


> I'm also in the same camp as George. I haven't got the means to stringent scientific testing, however anecdotal evidence in this hobby goes along way (as long you know what you're doing). I have used different spectrum bulbs and there hasn't really been a different in plant growth or formations in the leaves. Again, aquatic plants are opportunistic weeds, that have the ability to adapt to different situations. It's survival of the fittest.


 
What do you make of the above paper?


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## BigTom

Troi said:


> What did you make of the above paper?


 
I spend pretty much zero time worrying about this sort of thing (I neglect my plants and they still grow faster than I would like), but the paper isn't terribly conclusive. Some of the spectral results sound interesting but it only looks at one plant species for 2 weeks, with very small Ns and only the red light effect on branching looks particularly significant; there's no effect on fresh weight and again only the red light (which is a fairly extreme example in hobby terms) really shows much effect on anything else.

In so much as I'd read anything into it, it seems to largely support what Clive said -



> You have in fact, NOT been reading that spectrum doesn't matter, or that there are no effects of spectrum. What you've reading is that spectrum has negligible effects on plant growth rate and overall health


 
I will admit that I'm pretty crap when it comes plant biology though; generally I'm happy for the like of Clive and Darrel to do this sort of thinking for me (Matrix 2.0?!).


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## Ian Holdich

It would be interesting to get some backgrounds on the authors. A lot of these papers also seem to be quite old, I know that doesn't change the way plants photosynthesise, but advances in research techniques do improve. That said, it is an interesting read, but we could do with another up to date piece of evidence.


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## Tim Harrison

I don’t think we need to worry too much about the date the paper was published - 1977 (reposted below for convenience), and I am sure that the research was conducted with appropriate scientific rigor. But maybe Tom Barr will be able to vouch for the above since he may have been taught by these guys; he has an MSc in Botany from the same university - University of Florida Gainesville

From what I can gather, the spectral response of different plant species is variable, but in this case the quality of light is important not only to plant morphology but also to the rate of biomass accumulation. The figures in Table 3 are the results from 5 weeks growth and are pretty significant (dry weight is a more reliable method of measuring plant growth than fresh weight).

However, perhaps it usually isn't an issue for us hobbyists because the bulbs we tend to favour probably emit enough light of appropriate wavelengths for photosynthesis to occur at a rate that allows for healthy plant growth. Beyond that I suppose it doesn't matter what bulbs you use, actinic, day light etc.

Note the research also explains why plants are often found to grow well under actinic lighting because its spectrum peaks around 420 nm (blue light), which after red light yields the best growth.

http://www.apms.org/japm/vol15/v15p29.pdf ...Effects of Light Quality on Growth and Chlorophyll Composition in Hydrilla (1977, T.K. Van et al)


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## ceg4048

Troi,
	   The  thing we need to consider is that the tests in that paper were done with the color constraints of white as a reference and then with only red, blue, and green. They used filters which narrowed the transmission to very tight wavelength tolerances, though they do mention that there were some leak-through of other colors. They really had difficulty in isolating the colors and probably we would have seen wider margins of dry weight had they been able to do a better job of separation.

However, the fact remains that no one uses bulbs that are only red or only blue. All the bulbs we use have all colors. They all count as white light, so we will not see the same level of color isolation from bulb to bulb because all the bulbs we use simply have a different mix.

So this is something totally different than comparing Kelvin or comparing the spectrum performance of different bulbs. As I said, do the test yourself with different bulbs and without color filtration, and no matter which bulb you test, you will not see any difference in growth or health.


Cheers,


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## Troglodyte

I have to agree with Ceg4048 and Ian to a degree. I believe that the information on the paper is dated and science has probably moved on from that position or at least developed from that position held.  The content may be still relevant but as an experiment it is hardly conclusive. However if they had used LED light, then it could potentially be more relevant (if the correct LED colours are used only the colour used is in the spectrum) and I believe there are more papers available that have done this. 
One thing I always find personally, is that there is a missing link between the latest scientific knowledge/position and the information available to the general public. There does not appear to be any suitable linking mechanism from one to the other. If this was cracked, then it would allow people to gain more insight and produce more indepth contributions from a topic point of view.
The forum that can make this linking connection, will be the one that will prosper, as it will be able to support information factually, that people can have confidence in. This is not to have a dig at anyone that has done things through reptition of practice. As this is required also. However it allows many other factors to potentially change/creep into the results, or duplicates the ingredients of the contents of the replication in the first instance without knowing it.						
However we all have to accept that our knowledge today may not be 100% correct and may alter slightly when other discoveries are being made. Lighting is one of those subjects, I believe, that will be evolving as more is learned and released to the general public. Also do keep in mind that all plants are different, they have variable lighting requirements which supports the theory that, the "correct" lighting may be a variable that is unachievable in a mixed planted tank? This would also support the point that the plants (or aquatic weeds) will adapt to any lighting and environmental conditions available, if they are to survive.


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## ceg4048

Hello,
		 It's not really clear exactly what you disagree with. It's certainly a fact that none of us know 100% of the real facts. Those of us who have grown plants successfully have come to the realization that it really doesn't matter what type of lighting is used, and that what's more important, by far, is that whatever lighting is used, it's much more important to avoid using too much. None of the fluorescent bulbs have demonstrated any superiority over their rivals. They all contain blue and red, which are consistent with the fundamental frequencies of the chlorophyll response curves. The remaining colors in the spectral characteristics of the bulb are handled by the auxiliary pigments produced by the plants, which transfer their energy to the chlorophyll complex.

There is also no definition of "correct". If you can grow a plant to satisfaction, wherein the plant is healthy, is algae free, has acceptable growth rate and is not suffering any malady, then can this be considered correct? If this can be achieved with a variety of color combinations then why limit one's self to a particular color combination?

Hobbyists gain confidence when they follow the instructions and are later rewarded with success. Folks do not enter the hobby because they want to study the latest science of lighting. They simply want to grow plants trouble free. But the world has too many myths and hobbyists often fall prey to those myths. The biggest myth in planted tank lighting is that 6500K is correct. This is simply not true and that has been demonstrated many times.

With the advent of LED fitted with specific color diodes it may later be shown for example that since color isolation becomes possible, we will be able to reproduce the efforts in that journal article. So, for example, when initially flooding a tank, it may be possible to give the plants a head start by restricting the color to only red. Again, this is something that has to be tested and verified in someones tank, or groups of tanks fitted with LED. If you have actually performed these tests in actual tanks and have results to share then we're definitely interested in seeing those results. We really don't need to be scientists to do these tests. We just have to make sure that the test process is a scientific one.

As it stands now, what we observe in out tanks consistently, is that there is a much greater impact to the health of the plants from application of CO2, nutrient levels and flow distribution and maintenance practices than any effects due to spectrum. The health of the plants and the growth performance is the result of a combination of things that we do. Some factors are more important than others and the effect of any one factor can be mitigated by careful adjustment of the other factors, so really, there is no overriding priority to find "correct" spectrum.

Cheers,


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## Troglodyte

Good Morning Ceg4048,
Sorry for the confusion, what I was trying to say, is that I feel my thoughts align currently along the lines of what you and Ian are saying. However the limits are within our current knowledge which may not be 100% of what is factual happening. I have a tendency to be cautious over making statements on my present knowledge, due to the changes in the science and technical discoveries that improve our knowledge on a daily basis, it can sometimes come back and bite me in the bum later. 
I agree that the world of fishkeeping has many myths and these need to be put to rest quickly and I am sure with sites like this they will. However I do feel that the lack of connection between sites like this and the scientific communities out there prevent the myths from propagating more quickly into folklore.  I agree that teaching newcomers has to be a priority on this site and with a well laid out basic understanding of the facts, it should prevail into common knowledge. However I am sure you will agree, there are many intelligent individuals also present here, that would like to expand their knowledge and understanding through conversation and learning in a more light hearted manner than possibly following laid out instructions.(no matter how good the advice)
I do know there are papers out in the internet that discuss LED lighting experiments. I will be happy to look out for the ones I have read, but i am unsure as to the legalities of reproducing others work on commercial websites? Maybe I could do a review of the information, to bypass it. 
The LED experiment has already been done, to some extent and I will try to get a paper to support this claim with the above caveat in mind. I agree there may appear to be no overiding factor to gain the correct spectrum. However there may be an optimum lighting condition, that provides the best results of all the main important mitigating factors. 
Regards


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## ceg4048

Hi,
	You can easily link to the paper or quote the information from it as long as the source allows reproduction. If direct reproduction is disallowed then it might be better to simply paraphrase or to summarize as you suggest. Of course we need to know who is doing the experiments so that we can understand if there is possibly a bias.

Cheers,


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## lurch1000

Glad I found this. There's much talk of spectrum the world over as mentioned, and each time someone links to a spectrum, I don't see vast differences (on the whole) between many. I understand spectrums in terms of transmission values, but only for HD cameras.

The LED side of this intrigues me, and looking forward to the references. As a side issue I'm interested why even some manufacturers say that their LEDs are no good for plants - have they been sucked in to the spectrum legend? I'd go LED if long enough units were cheap enough - low running cost, and hopefully less heat in to the tank. Got a 2' tank, love a nice cheap LED clip over unit for it.


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## Tim Harrison

ceg4048 said:


> Troi,
> The thing we need to consider is that the tests in that paper were done with the color constraints of white as a reference and then with only red, blue, and green. They used filters which narrowed the transmission to very tight wavelength tolerances, though they do mention that there were some leak-through of other colors. They really had difficulty in isolating the colors and probably we would have seen wider margins of dry weight had they been able to do a better job of separation.
> 
> However, the fact remains that no one uses bulbs that are only red or only blue. All the bulbs we use have all colors. They all count as white light, so we will not see the same level of color isolation from bulb to bulb because all the bulbs we use simply have a different mix.
> 
> So this is something totally different than comparing Kelvin or comparing the spectrum performance of different bulbs. As I said, do the test yourself with different bulbs and without color filtration, and no matter which bulb you test, you will not see any difference in growth or health.
> 
> 
> Cheers,


 
Exactly...I think that is what I said...so in that we are in agreeance. The paper provides conclusive evidence that in the case of hydrilla, at least, spectrum does in fact have a significant impact on morphology and growth rate.

Confusion arises because what is often meant when it is said that spectrum output isn't important to plant growth is that there is very little difference between specialist T5 bulbs that manufacturers claim enhance plant growth and the cheaper alternatives...(colour temperature  aside, which is a different but related issue).

The two are very different propositions and I think that in future we need to be careful before making potentially misleading statements. In other words the statement "spectrum doesn't matter" needs qualifying, and I think that this has now been done.

But just in case there is any residual confusion, I'll repeat what I stated in my previous post...

..._Spectrum does matter to plant growth but it is not necessarily something that we as aquatic plant growers need to worry about because the bulbs we tend to favour probably emit enough light of appropriate wavelengths for photosynthesis to occur at a rate that allows for healthy plant growth_.

At the risk of confusing the issue, but with the hope of providing further clarification...This is supported by the increasing use of PAR meters rather that LUX meters. PAR meters allow us to compare or gauge how efficient our chosen lighting is at reproducing the spectral range designated as photosynthetically active radiation (PAR)...the clue is kinda in the title.

In short, if spectrum were not important to plant growth why bother using a PAR meter?


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## mi5haha

bulb manufacturers have been demonstrating the "ideal" wavelength of their "growth type" bulbs all the time. So the peaks in blue and red spectrum sensible to plants mean something or nothing?


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## Tim Harrison

With reference to my above post yes they do mean something...but perhaps not as much as manufacturers would have us believe in relation to their particular branded bulbs. And in particular since the cheaper alternatives we favour probably emit enough light of appropriate wavelengths (red and blue light) anyway.


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## lurch1000

Manufacturers will make available what is in demand, so if a plants are said to need peaks at x y and z wavelengths, then they're going to supply the demand. If a renowned planting guru stated that this new wavelength worked and this nobrand tube delivered it, Arcadia and all the others would start making a tube to suit.

I think Troi has hit the nail on the head, does spectrum matter in the aquarium generally? I've never looked that closely in to it as I've never been that concerned, I've either run with what the tank came with, or what suited my wallet or eye.


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## lurch1000

(Sorry Troi, didn't see your interposed post before I hit send)


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## ceg4048

Troi,
	   The issue of peaks is also part of the spectrum argument and it should be addressed. Peaks are irrelevant because they do not tell you anything other than the energy contribution at a specific wavelength. As demonstrated by this very question, spectral curves are not at all understood and that's another reason their relevance is questionable. People don't realize, when assessing the value of the curve that the energy of wavelength groups is dependent on the area under the curve, not the peak value, which is meaningless. There are no plants that "require" peaks anywhere.

Furthermore, it is the area under the curve that is most closely related to PAR, so that's why a PAR meter is relevant.

While manufactures can be said to produce what is in demand, as it turns out, they are the ones telling folks what they should be demanding. We see this every day. And what is in demand when it comes to lighting freshwater tanks is not necessarily what should be in demand. People have not be demanding so-called 6500K bulbs just because they knew anything intrinsically. They were told that they needed it and so they demanded it. An illusion of the highest order.

That is why spectrum is much more a sociological issue than it is a scientific one. The problem is that generally, many do not understand the rudiments of plants and neither do they understand the rudiments of light. That's why I continue to maintain that we need to test for ourselves. We have already seen that the experiments listed in the link had only very limited relevance to us even though the data, results and conclusions seem to suggests otherwise.

One can say that wavelength or frequency matters, but spectrum, by it's very definition (a band of colors), as it applies to a planted tank, does not matter. On the other hand, PAR, regardless of spectrum, matters. PAR determines the rate of growth because it relates specifically to the energy input to a photosynthetic organism, and photosynthesis is, by definition an energy conversion mechanism.

Cheers,


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## Tim Harrison

I agree...I think - that is if I understand you correctly...in so much as the peaks just demonstrate the effectiveness of different wavelengths of light in driving photosynthesis. That is why the peaks correspond most markedly with the absorption spectrum of chlorophyll _a (wavelengths below 500 nm - blue light, and above 600 nm - red light). So in this respect spectrum does matter._

PAR designates the "spectral" range, or if you prefer "wave band", of solar radiation from 400-700 nm that organisms are able to use in the process of photosynthesis. As far as I understand it PAR meters are weighted specifically to tell us whether our plants are receiving enough light of the right quality to promote efficient photosynthesis.

The results of the paper are very relevant to us as aquatic plant growers but its something we need not worry about because on the whole the bulbs we tend to use e.g. full spectrum HO T5s output enough PAR to ensure that our plants grow well and remain healthy. That is also why manufacturers claims regarding special growth type bulbs as opposed to the cheaper alternatives are perhaps more than a little overstated.


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## ceg4048

PAR is much more than a designation of range. Any light in the visible spectrum is usable. PAR is a measurement of the number of photons crossing a unit area per unit time. It is the number of photons that strike a pigment molecule per unit time, combined with the specific energy gain of the electron that determines the effectiveness of the light. It has nothing to do with wave or band because the property of the light that is relevant to photosynthesis is the particle property of light. The particle property determines the number of particle collisions with the chlorophyll's valence electron. The wave property determines the energy inherent in each collision. Light is both particle and wave, and each of these properties are responsible for the reaction with the pigment molecules.

When you see a sharp peak in a spectral graph, this is just a record telling you that there are some photons having a specific energy level present in the storm. But those photons alone do not determine the total number of collisions and the total energy being seen by the leaf. The leaf sees the sum total of all the photon particles at all the wavelengths shown under the curve. The amount of energy delivered by the photons in the peak is very small compared to the total amount. So sharp peaks are meaningless. If the peak broadens out and produces a wider area then that tells you there are more photons of that frequency present in the storm.

I think that is what you are missing. If you review the article you'll see that the only way they could compare the performance of the individual colors was to raise or lower the light so that the PAR for each color was the same. That alone should tell you that PAR is important, because when the PAR values were equalized it means specifically that the same number of photons were crossing over the same amount of area in the same amount of time.

So, they equalized the "photon flux density" to 30 microeinsteins per square meter, per second. That means 1,806,000,000,000,000,000,000 photons (1,806 billion billion) individual particles were crossing over one square meter every second.

When they used the blue filter, about 50% of those particles (903 billion billion) each were vibrating at 1/300,000,000,000 or 3.3 trillion times per second. The other 903 billion billion photons were vibrating at slightly different speeds. That's what the wavelength means. The energy inherent in some particle vibrating at 3 trillion times per second collides with an electron and that particle is annihilated. All the energy that was that vibration is now given to the electron and it is this electron energy that allows it to escape the bond of the chlorophyll to be used in a chemical reaction.

So that's what PAR tells you. It tells you exactly how many possible collisions can occur. You cannot dismiss PAR as some kind of vague "wave band" or "quality" or "promotion". That is a complete misunderstanding of the data.

Here is what's actually relevant about that article. In fact it's so relevant that it is completely mind blowing and nobody is actually paying attention because they are too busy being fixated on vague "wave bands":

Red photons actually have the lowest vibration energy. They have the highest wavelength (680) and thus the lowest vibration frequency. In electromagnetic fields, the higher the frequency, the higher the energy. That's why microwaves and X-rays and Cosmic rays will kill us outright. They have the smallest wavelengths and therefore the highest frequency.

One would expect that blue light, having the higher frequency, and chlorophyll having a higher response to blue should generate the higher growth rate, yet, look at the data, the frequency that generated the highest growth rates is the lowest frequency, the lower response of chlorophyll and the lowest energy level. Think about that for a minute and think about the implications. So the question we should be fixated on is: WHY?

Cheers,


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## Ian Holdich

I want Clive's babies.


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## Tim Harrison

Absolutely, any light in the visible spectrum is of course usable since both PAR and the visible spectrum are one and the same, give or take a few nm.

Sure the peaks don't tell the whole story and this is where accessory pigments come in to play and why compared to the peaks in the absorption spectrum for chlorophyll _a_ the peaks in the action spectrum are broader and the valley narrower and not as deep. This was observed by Thomas Engelmann in 1883.

And thanks for your treatise on PAR, but I think that perhaps the issue is becoming unnecessarily complicated. The bottom line is that many of us go to great lengths to ensure no limits to plant growth in our aquariums whether we're discussing fertz dosing, CO2, or indeed as on this occasion artificial lighting.

Whichever way it's spun, put simply, spectrum is important to plant growth. For instance, if deficiencies in the blue and red wavelengths become limiting factors to growth the plant is forced to compensate, maybe through the production of more chlorophyll and accessory pigments. And this is not particularly good news since in the words of the Tropica boys...

'...Adaptation to resource limitation is a costly affair. Whether the plant invests in more chlorophyll or more enzymes it results in higher nutrient requirements and higher energy use. The higher energy use comes from the fact that proteins require constant maintenance in the cell to work properly and these maintenance processes absorb valuable energy and carbohydrates, which might otherwise be used for growth purposes...'


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## lurch1000

Interesting to read the different viewpoints here.

Question is, in the typical aquarium, say 60cm from top to bottom, will any white bulb that has something in the red and blue spectrum near the alleged peaks be able to deliver the required energy through what is basically shallow water? Even with T8 lighting, what will the reduction of intensity be after punching through 2' of water? Might go see if I can find the box for my Interpet Community Daylight tube for my old tank. See what the spectrum was for a non-plant tube.

Colour temperature, IMO is irrelevant, buy the colour you think suits your tank, to a point.


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## ceg4048

Troi said:


> For instance, if deficiencies in the blue and red wavelengths become limiting factors to growth the plant is forced to compensate, maybe through the production of more chlorophyll and accessory pigments.


And so what? When have you ever seen a deficiency in blue or red? This never happens. When people have problems in a tank, virtually 100% of the time the problem is due to having too much blue, red and other colors. I have never seen any deficiency of blue or red photons using any of the bulbs, whether using cheap Tesco or expensive "plant" bulbs.

The quote you lifted applies to all resources, and especially applies to CO2, which is the prime limiter in a tank. When we are solving health issues in a tank, it is actually necessary to intentionally limit the photon flux, because the health issue is usually caused by a resource limitation other than blue or red photons, and the abundance of those photons makes the situation worse. That is a certainty. And if people continue to worry about a resource being limited, when in fact that resource in question is actually in overabundance, then they will continue to have problems, and they will deserve their misery. There is so much more to worry about in a planted tank that it renders spectrum academic. Gas exchange is 10,000X more important to plants because gas diffusion under water is 10,000X slower. Photons do not have any trouble finding their way to the bottom of the tank, so this is never a problem. Plants grow because of gasses. Their growth behavior is only mediated by the characteristics of the photons.



Troi said:


> And thanks for your treatise on PAR, but I think that perhaps the issue is becoming unnecessarily complicated.


I went through great lengths to address a complicated issue in the simplest way I could. If you want to simplify it even further, then just don't worry about it because you will never see a limitation of red and blue when using fluorescent lighting, no matter what bulb or what spectrum  you choose. That's what we have been saying all along. If someone wants to use LED and isolate the spectrum to all red or all blue, then good luck to them, but I wouldn't want to spend my viewing time looking at a red tank just because the article shows that red produces a higher mass increase rate than white.

All these arguments about how spectrum is so important are false because no one has ever demonstrated the results of red starvation or of blue starvation in a standard planted tank, using standard lighting. As I mentioned in my first post, the data from these experiments have to be related to be within the context of our tanks. The data is useful and instructive of course, but one cannot find correlation to the system we have in place. You will never see a 70% difference in growth rates in 5 weeks using any of the bulbs we have at our disposal as you saw in the article. In fact, the differences between the bulbs will be imperceptible. That's how different our situation is from theirs. Again, you have to try it and see for yourself, not assume that because the article derives a conclusion then it automatically applies, because you do not know of, and have not accounted for, all the anomalies of the tank compared to their setup. Have you considered for example that plants in the tank will reflect inbound light and will change the local spectrum in their vicinity, that the spectrum profile in a tank is not static and is not equal? Have you considered that the plants response to a color is actually modified by the presence of other colors? This is so complicated, and the gains are so minimal, that it isn't worth worrying about.

Cheers,


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## Andy Thurston

I got some 8w t5 6500k daylight tubes from a lamp supplier in leeds for £2 each. arcadia tropical daylight are £10+ 
Im gonna use em now and see what happens cos i wont mind replacing them every 6-8 months and if plants grow without unwanted algae then i wont think twice about using them in another  tank


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## DrRob

I've long wondered about spectrum and, from my own experience, noticed one very simple thing, which is that with spectrums between 6500K and 10000K I'm happy with less overall light output and I always want something brighter if I go outside of that range, which means that I end up with algae. Anecdotal, I know, but it's worth considering the human element on lighting intensity choice beyond what the plants are doing, as we're all prone to tweaking things to look nice rather than grow well if we're not careful.


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## Andy Thurston

Wouldnt plants be used to different spectrums of light over the course of the day and year anyway? 
After all our light is filtered by our atmosphere, which is constantly changing with weather pollution etc
 Ive also read of people using 6500k houshold daylight tubes from hardware stores in states without any problems 
 Could it be like undergravel heating where it makes a minimal difference, if any, to overall plant health? And we are being blinded by an explanation too complicated for average fishkeeper to understand with no figures to back it up


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## dw1305

Hi all,


Big clown said:


> I got some 8w t5 6500k daylight tubes from a lamp supplier in leeds for £2 each. arcadia tropical daylight are £10+ Im gonna use em now and see what happens cos i wont mind replacing them every 6-8 months


Keep the £2 ones, they are fine as tubes and you don't need to change them until they stop working. Electronically ballasted T5 tubes show very little "lamp lumen depreciation".

Have a look at these links: <Do T5 lamps have better lumen maintenance than T8 or T12 lamps? | What are T5 Lamps? | T5 Fluorescent Systems | Lighting Answers | NLPIP> & <Do t8 lights really degrade over time? | UK Aquatic Plant Society>.

cheers Darrel


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## Tim Harrison

ceg4048 said:


> And so what? When have you ever seen a deficiency in blue or red? This never happens. When people have problems in a tank, virtually 100% of the time the problem is due to having too much blue, red and other colors. I have never seen any deficiency of blue or red photons using any of the bulbs, whether using cheap Tesco or expensive "plant" bulbs.Cheers,


 
Hi Clive
This is becoming amusing. I think we’re now arguing at cross-purposes and on a point of pedantry. Nevertheless, I couldn't disagree with you less on all of your points, but especially on the one above.

I said a while back that spectrum does matter to plant growth (blue and red light work best for photosynthesis, while green is the least effective colour). However, its not something we need necessarily concern ourselves with as aquarists since the broad spectrum bulbs we tend to favour (those aesthetically pleasing to the eye) probably output enough light of appropriate wavelength to ensure healthy plant growth. I think I must have stated this several times now.

I just objected to the somewhat abstract and sweeping generalization “spectrum doesn't mater”, and I went about trying to qualify that statement. Which I hope I’ve/we’ve now done.



ceg4048 said:


> The quote you lifted applies to all resources, and especially applies to CO2, which is the prime limiter in a tank. When we are solving health issues in a tank, it is actually necessary to intentionally limit the photon flux, because the health issue is usually caused by a resource limitation other than blue or red photons, and the abundance of those photons makes the situation worse. That is a certainty. And if people continue to worry about a resource being limited, when in fact that resource in question is actually in overabundance, then they will continue to have problems, and they will deserve their misery.Cheers,


 
Yes you are right the quote applies to all resources. And for the most part I am sure you are also right to suggest that most problems arise due to inadequate CO2 and too high a light intensity, as you frequently do. However, many demanding plants for instance _Hemianthus callitrichoides_ ''Cuba'' require high light and high CO2 etc to thrive.

So just as many a person has failed to grow the plant because of inadequate CO2 I am sure that there are many that have failed due to inadequate light intensity as well, or both. This and other similarly “advanced” species obviously do not adapt to resource limitation very well. So again we need to be careful not to appear, at least, to promote one or the other resource as a panacea without qualification.



ceg4048 said:


> I went through great lengths to address a complicated issue in the simplest way I could. If you want to simplify it even further, then just don't worry about it because you will never see a limitation of red and blue when using fluorescent lighting, no matter what bulb or what spectrum you choose.Cheers,


 
I’m well aware that photosynthesis is a quantum process, but I’m also aware that although modern science has become very technical it is still possible to describe it in a way that people without scientific training can understand. To be frank I’m very scientifically trained and I had difficulty understanding your explanation of PAR.



ceg4048 said:


> Have you considered for example that plants in the tank will reflect inbound light and will change the local spectrum in their vicinity, that the spectrum profile in a tank is not static and is not equal? Have you considered that the plants response to a color is actually modified by the presence of other colors? This is so complicated, and the gains are so minimal, that it isn't worth worrying about.Cheers,


 
Yes being scientifically trained I had considered the above. However, I have also considered that the authors are very eminent professors in their chosen field of endeavor from a university with a global reputation for excellence in the same. Further, the paper was published in a very respected journal (J. Aquat. Plant Manage.; (United States); Journal Volume: 15) and would have been peer reviewed by other eminents in the field. Therefore, the research would have been conducted with appropriate scientific rigour; and far more so than any homemade experiment could hope to replicate.



ceg4048 said:


> Here is what's actually relevant about that article. In fact it's so relevant that it is completely mind blowing and nobody is actually paying attention because they are too busy being fixated on vague "wave bands":
> 
> Red photons actually have the lowest vibration energy. They have the highest wavelength (680) and thus the lowest vibration frequency. In electromagnetic fields, the higher the frequency, the higher the energy. That's why microwaves and X-rays and Cosmic rays will kill us outright. They have the smallest wavelengths and therefore the highest frequency.
> 
> One would expect that blue light, having the higher frequency, and chlorophyll having a higher response to blue should generate the higher growth rate, yet, look at the data, the frequency that generated the highest growth rates is the lowest frequency, the lower response of chlorophyll and the lowest energy level. Think about that for a minute and think about the implications. So the question we should be fixated on is: WHY?Cheers,


 
Going back to the above quote from your explanation in the previous post, and your question WHY? I agree it is remarkable that despite all, red light did produce the greatest growth rate. However, what you’re missing is that the plant grown under red light had the highest chlorophyll _a_ content. Maybe that made all the difference.

Regardless, I think though from our point of view it would perhaps be interesting to consider that the compact and bushy growth that many of us find attractive is largely due to the red part of the spectrum, as implied by the experiments results.


----------



## ceg4048

Troi said:


> I just objected to the somewhat abstract and sweeping generalization “spectrum doesn't mater”, and I went about trying to qualify that statement. Which I hope I’ve/we’ve now done.


Hi Troi,
  This generalization is, in my opinion, a much better way to think about lighting because in order to consider relevance, one has to in effect take the factor being studied into consideration in terms of how one will execute their processes. So you have to ask yourself, what type of bulb will I need to restrict myself to, or what bulbs must I now avoid due to their lack of performance. In the real world, the answers are: No restrictions and No avoidance. The reason being that none of the bulbs in question have a marked improvement over any other bulb. Therefore, within the context of our tanks, there is no relevance because there is no bulb you can buy that does not have sufficient blue and red.

So lets take a look at some of the hypotheses you offer which might have relevance:



Troi said:


> However, many demanding plants for instance Hemianthus callitrichoides ''Cuba'' require high light and high CO2 etc to thrive.


No, this is not true. I and many others can and have grown HC with low-to-middling light. That HC requires high light is another construct of The Matrix. People think that they need high light because they were told this. So they add lots of light, do not pay attention to flow and CO2, and the result is meltdown. While there is little doubt that HC has a higher light compensation point than say, Ferns, the LCP for HC is not very much higher than it is for Ferns. Even if it's 100% higher that just means that a Fern will grow at PAR levels above 10 micromoles and that HC will grow at levels above 20 micromoles. This is not very high at all. But no one uses 20 micromoles. It's just too dim aesthetically, and the HC will take forever to grow.

I think people mistake growth rate with health. You can throw tons of PAR at a plant and it will grow faster. We already know that. So, if HC is grown at a PAR of 100micromoles, and if flow/distribution and CO2 is adequate the plant will look lush and beautiful very quickly. If the same plant is grown at a PAR which is just above LCP then it will take a very long time to reach that lush state  - but it will get there eventually, and it will be just as healthy. But no one wants to wait forever, so they pummel the plant with high light and THAT'S WHY there is so much failure with HC. I don't have ANY trouble growing this plant at low lighting levels. George Farmer has no difficulty, Dan Crawford, Mark Evans and Tom Barr have grown this plant at low lighting levels. It's only the Megawatt Loving Klingons (MLK) who have difficulties with HC. Also, as mentioned by George, there has been no perceptible differences in growth rates or in health based on the various fluorescent bulbs used. I've used standard office bulbs and even splurged for Grolux (which are high in Red and Blue) George likes fancy bulbs but he has also used cheap bulbs without difficulties.

Oh, and by the way, those fancy ADA bulbs? It turns out that they are very high in green, and it turns out that their ballasts produce 2X-3X less PAR than other ballast. When you see those fantastic Amano gallery shots, the lighting used to take the photography might be high but the plants are actually grown under low lighting. In the flesh the tanks look bright because the human visual cortex has it's response peak in the green. So here is an entire industry centered around a color band that has the lowest performance according to the article. Does it matter one iota to their ability to produce amazing tanks? No!



Troi said:


> Regardless, I think though from our point of view it would perhaps be interesting to consider that the compact and bushy growth that many of us find attractive is largely due to the red part of the spectrum, as implied by the experiments results.


No, this is not worth considering either. Compact and bushy growth is a function of the ability of the plant to rid itself of the gaseous hormone ethylene. This is yet another myth. This is specifically WHY I continue to harp on the importance of flow and distribution. But people don't really want to hear about that because it's another difficult concept to grasp, so it's easier to talk about spectrum.



Troi said:


> I am sure that there are many that have failed due to inadequate light intensity as well


No, the people who report this only THINK that they failed due to low lighting. They simply did not understand the truth. I think you're forgetting that we collectively have the empirical data, not only in our own tanks, but in tanks around the world where people ask our opinion and we provide instructions on which factors to ignore and which to pay attention to, and we have a pretty good success rate, so we constantly see the results, which reinforces what we understand to be the truth. Is there a possibility that there are other factors we do not yet understand? Absolutely! But one thing is for sure, it's very easy to disprove a theory, and this theory of how spectrum is significant to the way we grow is very easy to disprove.



Troi said:


> I’m well aware that photosynthesis is a quantum process, but I’m also aware that although modern science has become very technical it is still possible to describe it in a way that people without scientific training can understand. To be frank I’m very scientifically trained and I had difficulty understanding your explanation of PAR.


Most likely there are two factors in the inability to grasp. The first might be that there is a preconceived idea about what light itself is and that conflicts with the preconception. Another contributing factor might be that there is a lack of understanding about how plants actually use light. Let me offer this as a clue:
When God said "Let there be Light" he did not mean "Let there be a lamp switch that folks can flip it so that light will enter their dark room". What he meant was "Let there be a reality and a Universe whose very construct is based on the properties of light as it's fundamental participles of existence". It turns out that we are actually the servants and the children of light.

So, in now way am I dismissing the importance of spectrum and in no way have I implied that there is no relevance to spectrum. What I have stated is that the things that we are using to measure the importance of colors in our tanks is of little value and is in no way indicative of the importance of color, and that using the bulbs we have at our disposal, the effects of color are not to be seen in our tanks in the same way as that demonstrated in that experiment.

I have not denigrated the ability of the professors or of the journal in any way. What I have said is that their focus and priorities will not necessarily match our priorities and so it is important to understand the context of the article. Even though we learn something, the data may not apply to us.

We should be feeling liberated about this. We should not be pensive. We can use colors in any manner we chose without fear of ill health. I love playing with colors and seeing their aesthetic effects on the tank and the fish. We should view the spectrum as a way of enhancing the aesthetic appeal of the tank and we need not handcuff ourselves thinking about what colors we can or should use just because it is less than "optimal".

Cheers,


----------



## Tim Harrison

We're now entering in to the realms of philosophy, and the argument has become somewhat circular, so I don’t really have anything further to add short of repeating myself again. Nevertheless, since we’re becoming philosophical I think, all things considered, those of us that find growing plants relatively easy perhaps take it for granted and don't necessarily fully understand the process we undertake to do so. In other words, some of us find it intuitive and therefore maybe draw the wrong conclusions when attributing success.

I think the amount of light used often has more to do with compensating for quality through quantity and that the benefit of “red” light, for example, is perhaps underestimated. Perhaps red light has more to do with producing the desired growth rate and plant morphology, which we find so attractive, than current wisdom would have us believe. Maybe this is why the actual amount of light that many successful "advanced" layouts use is often well in excess of 1 watt per litre of T5. And why anecdotally different T5 bulbs don't appear to have any discernible influence on growth, especially since they are often raised or lowered to achieve a desired PAR.

Like I said, I can find much in your philosophy to agree with, and I'm glad that, generally speaking at least, you finally agree spectrum matters after all, especially in "light" of the high cost of adaptation to resource limitation. But by the same measure I find some of what you say incomprehensible and contradictory. For instance, I agree that flow and distribution are important but it’s not the whole story, especially with regards ethylene. Spectrum and light intensity are important too. Plants will produce ethylene in response to low and/or poor light conditions. Ethylene causes etiolation which allows the plant to quickly reach less attenuated and/or brighter light nearer the surface. The result is an unattractive and weedy plant; the opposite of what we're all trying to achieve.

Anyway, I'm sure time will tell. Until then I will endeavor to keep an open mind…


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## dw1305

Hi all,


ceg4048 said:


> We already know that. So, if HC is grown at a PAR of 100micromoles, and if flow/distribution and CO2 is adequate the plant will look lush and beautiful very quickly. If the same plant is grown at a PAR which is just above LCP then it will take a very long time to reach that lush state - but it will get there eventually, and it will be just as healthy. But no one wants to wait forever, so they pummel the plant with high light


Good things come to those who wait. Low light, low nutrients gives you stability, and I would always rather have stability than rapid growth. <220 litres of failed ambitions - open to constructive criticism | Page 2 | UK Aquatic Plant Society>


Troi said:


> For instance, I think the amount of light used often has more to do with compensating for quality through quantity and that the benefit of “red” light, for example, is perhaps underestimated. Perhaps red light has more to do with producing the desired growth rate and plant morphology, which we find so attractive, than current wisdom would have us believe.


Troi you are right you can definitely manipulate plant morphology with different wave lengths of light. If you have a look on the forums where people grow "Tomatoes"* hydroponically under grow-lights, you'll find there is a huge amount of data about PAR, wave lengths and growth morphology

*other species of plant may be available

cheers Darrel


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## Tim Harrison

dw1305 said:


> Low light, low nutrients gives you stability


 
I agree



dw1305 said:


> Troi you are right you can definitely manipulate plant morphology with different wave lengths of light. If you have a look on the forums where people grow "Tomatoes"* hydroponically under grow-lights, you'll find there is a huge amount of data about PAR, wave lengths and growth morphology
> 
> *other species of plant may be available


 
Thanks Darrel, there is some very enlightening research going on, and it does indeed apply to other species of plants, infact as far as I understand it all angiosperms. Here's another paper I found; it's a bit involved but it's worth a read:
Light as a Growth Regulator: Controlling Plant Biology with Narrow-bandwidth Solid-state Lighting Systems 

This also is perhaps worth a read, the conclusion is quite revealing:
Green light: a signal to slow down or stop


----------



## ceg4048

Troi said:


> Plants will produce ethylene in response to low and/or poor light conditions. Ethylene causes etiolation which allows the plant to quickly reach less attenuated and/or brighter light nearer the surface. The result is an unattractive and weedy plant; the opposite of what we're all trying to achieve.


This is not the case for aquatic plants. The ethylene buildup is a result of poor gas diffusion from the plant. Ethylene is a gas and suffers the same fate as other gasses when submerged in that it does not diffuse well. In aquatic plants the ethylene buildup is one of the signals to the plant that it is submerged. In flood tolerant terrestrial species the ethylene signals changes in the root structure commonly referred to as "programmed death" of certain cells within the roots, of which the effect is to create void areas which are later used as gas exchange pathways inside the roots. Trees such as Mahogany and Fig in the tropical rain forests such as the Amazon use this mechanism to survive. Smaller plants which become submerged elongate to reach the surface where CO2 is present in abundance. The reason you find the information contradictory is because you are not taking water into account and you are ignoring the plant's adaptation to flooding by modification of those processes which serve land plants to solve the challenges of a hostile environment.

Again, this is another case where you are misapplying the data from terrestrial plants and blindly applying them to aquatics without ever taking into account the detrimental effect that the water has. All across The Matrix people are programed to think  in terms of aquatic plants loving water. The vast majority of the aquatic plants despise water, but they cannot just pick up and move when the rains come, so they have to make special adaptations to being flooded. Many of the plants that we have trouble with  are those that are rarely found totally submerged in water so they have never developed an efficient means of collecting and processing CO2, and, in their particular niche, they can deal with partial flooding because they have access to atmospheric CO2.

Here is another stock photo I use as a typical example in a natural system. This is a tropical grove of Bacopa in open area. The PAR levels here are around 2000 micromoles. Look at these plants carefully and you'll see that the leaves that are browned are only those that are submersed, and they are only a few centimeters from the 2000 micromole light. The leaves under water are annihilated by the sunlight. There is no shortage of light in this scenario. The leaves that are green and healthy are those that have emerged from the water and which have access to CO2. The submerged leaves have no access to CO2 because the water temperature in the shallows is very high, which drives off CO2. As soon as the water level rises due to rain the stems elongate. So in this case plants are not seeking more light, they are seeking more CO2.
This case more resembles our situation. The issue of light and spectrum are completely irrelevant because adding more light or changing the spectrum will not improve the situation when the resource limitation is CO2.





In other natural systems, the plants adopt the strategy of floating in order to maintain contact with atmosphere. Whereas in those  systems away from open savannah, where PAR is significantly lower, under shade, canopy or murky/stained water for example, the submerged leaves are able to eek out a living due to higher dissolved CO2 and O2 within the water column.

So one can dream up any scenario to justify belief in the significance of spectrum based on data that has limited applicability, but the imperative of gas exchange are the real life scenarios and they trump any significance of color. When we flood a tank the plants are immediately subject to an extremely hostile environment and they must make the adaptations or perish. If we are blind to these facts and if we focus our attention on things that do not help the plant to adapt then we contribute to the failure.


People worry all the time about whether they have enough light, and will the light they have be able to penetrate to the bottom of the tank, when actually, if you bother to take the measurements yourself, it will be revealed that a flooded tank has HIGHER PAR values than when  measured empty. A lot of that is due to reflections from the glass and from the underside of the  water's surface.

I see no contradiction in these basic truths. The fact of the matter is that when CO2 uptake is high less light is required. So one actually lowers the demand for light with high CO2. When we focus more on gas exchange and availability we will have a much higher success rate than if we focus on spectrum.

Cheers,


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## Tim Harrison

Jeez Clive...but you're hard work...

...Once again I find myself agreeing with you again but only partly, and I have to concede that my explanation was somewhat clumsy and you quite rightly picked me up on it. Yep a lot of the plants we like to grow in our tanks don't particularly like being submerged, and yes it is ethylene build up that is generally thought to be the prime instigator of submergence escape, but it's not absolutely conclusive, and some species use other signals such as partial lack of O2, or increase in CO2...believe it or not.

But it's not the whole story. Maintaining the faster elongation beyond the first few hours may involve factors not necessarily needed for the initial response especially in flood waters a few metres deep and for many aquatic species. Light may well be one of these factors and I think I have more than adequately demonstrated that its attenuation in water is capable of stimulating stem elongation.

So to sum up, undoubtedly flow and distribution are important but so is light...both intensity and spectrum (quality and quantity) and to ignore this because you consider that most people have too much light is missing the point somewhat and can be quite misleading. This especially so in light of the fact that spectrum has such a marked influence on the morphology of all angiosperms (higher plants), including the submerged ones.


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## bridgey_c

I don't want to interrupt a fantastic thread so apologies in advance...	but.....

If I can try and put your knowledge Troi into the real world, if you were setting up a tank tomorrow with 2 x t5 light bulbs, what bulbs would you use? (co2 injected +EI dosing)

edit - (given that you wanted the best plant growth)


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## Tim Harrison

I'm not sure whether this is a trick question or not I'm very tempted to suggest that I would splurge my, not so hard earned, cash on special growth bulbs just to be contentious. Especially since the evidence that I've unearthed overwhelmingly supports my supposition that spectrum matters, and maybe, just maybe, they might provide additional benefit to the type of growth we find attractive But I don't have the energy nor the time to go another several more rounds with Clive...he's exhausting

Truth is I actually do splurge out on Arcadia bulbs cause I like the colour rendition, they're good quality, and the local Dobbies garden centre does them at relatively knock down prices. However, like I have previously stated, most HO T5 bulbs that we find aesthetically attractive can also, by happy coincidence, provide plants with the quality and quantity of light that they require. It's a function of the fact that the photosynthetically active spectrum and the visual spectrum are one and the same give or take a few nm; although humans and plants perceive them slightly differently.

I think that the significance of spectrum will take a while to sink in, so, for the time being at least, I'll do what everyone else does and redirect you to this...Cheap HO T5 fluorescent tubes - Update with photos | UK Aquatic Plant Society


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## bridgey_c

It was a genuine question.. I promise.. lol ( but I see how it could ignite another fire!)

I ordered 4 bulbs of different kelvins last night just for fun... from £4 for a 4000k and 6500k bulbs to £11 for a sylvania grolux type.. It isn't a great deal of money and I will enjoy messing around with combinations to see how they affect the tank visually..

I think you both make great points... Sometimes the internet is a hard place to talk about such matters.. you would be better off meeting in a pub and chatting over a few pints sometimes!


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## BigTom

Troi said:


> ... maybe we can get some sort of discussion going ...


 


Troi said:


> But I don't have the energy nor the time to go another several more rounds with Clive...he's exhausting


 
Hehe, got to be careful what you wish for sometimes Troi 

Good thread though!


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## Tim Harrison

bridgey_c said:


> It was a genuine question.. I promise.. lol ( but I see how it could ignite another fire!)


 


BigTom said:


> Hehe, got to be careful what you wish for sometimes Troi


 
It's all got a bit too earnest. But I can't resist throwing another thought in to the gladiatorial arena...

...Clive mentioned that ADA MH lamps peak in the green part of the spectrum. They call the green peak a "sub-peak" and it's specifically designed to bring out the colours in the plants. But significantly they also peak substantially in the blue and the red part too. Check out the Tech Specs: 8000K HQI bulb.

Amano is on record as saying that he thinks the blue part of the spectrum produces the compact and bushy growth that help give his nature aquarium layouts their signature appearance. This is certainly corroborated by the scientific papers I’ve linked. Accordingly, it occurs to me although aquatic industry bulb manufacturers make big claims about the photosynthetic prowess of their specialist growth lamps - that are difficult to substantiate, and which may well be overstated - there may actually be an element of truth to those claims.

And what these bulbs actually do is, not necessarily increase growth rate, but, affect plant morphology (e.g. blue light = compact growth, etc), and that perhaps this hasn’t been noticed anecdotally because we’re all too busy looking for a miracle growth rate response.

But it’s just a thought that I think is worth considering...and given the scientific evidence a thought that perhaps aught not to be dismissed out of hand too quickly…


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## lurch1000

It's been a good few rounds hasn't it? 

Just to be contrary, I want to encourage algal growth in my new tank, what tube should I get? Got the option of fitting it to a 600mm T5 fitting, or an 18" T8... 

(That one is tongue in cheek just to be clear, but to many's horror, I will be attempting to culture algae!)


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## Andy Thurston

Thats easy 
As many lights you can get over tank no co2 poor circulation and youll be fine, but why?
It may be hard to grow specific types though


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## roadmaster

Was reading discussion's on APC,and the Krib that pointed to Dutch aquarist's, and some award winning aquascapes, that indicated that they seldom use bulb's over 5000 K.
Personally,,I have used 3500 K,4000K,5000K,6000K,6500K,6700K,and 10,000K bulb's and variation's/combination's thereof.
All of these grew plant's just fine in my opinion,so I am leaning toward's Ceg's contention.(opinion's vary)
For my eye's however,, I have settled on 50/50 6700/10,000 K CFL's.


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## Troglodyte

Good Evening All,
I must say this discussion is one that I have enjoyed reading.  I would like to say that both sides from Troi and Cegs to be very educational bringing about a proper discussion about the lighting subject in this forum. Nice to see guys well done  I believe it will be a healthier forum, for it, too. 
It does show though, that a lot of the information out there currently is related to land plants and more needs to be done in the way of aquatic plants. Although the point is taken that generally the same processes occur in both. I also do believe it now needs to reflect the aquarium environment too as this will validate the results more, for our use and benefits if any?
Keep up the good work guys.


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## plantbrain

Troi said:


> I said a while back that spectrum does matter to plant growth (blue and red light work best for photosynthesis, while green is the least effective colour). However, its not something we need necessarily concern ourselves with as aquarists since the broad spectrum bulbs we tend to favour (those aesthetically pleasing to the eye) probably output enough light of appropriate wavelength to ensure healthy plant growth. I think I must have stated this several times now.
> 
> I just objected to the somewhat abstract and sweeping generalization “spectrum doesn't mater”, and I went about trying to qualify that statement. Which I hope I’ve/we’ve now done.
> I agree it is remarkable that despite all, red light did produce the greatest growth rate. However, what you’re missing is that the plant grown under red light had the highest chlorophyll a content. Maybe that made all the difference.
> 
> Regardless, I think though from our point of view it would perhaps be interesting to consider that the compact and bushy growth that many of us find attractive is largely due to the red part of the spectrum, as implied by the experiments results.


 

Hopefully I can cut through some of the chafe and not add too much to it
I would never do that, hehe.

One of the main questions and unknowns I've long had is can we design a wavelength set that will optimize the growth vs minimizing the energy input?
PAR vs PUR.

Will all 400 aquatic plant species be the same?

Can we say such things and generalize like this?

Clearly not.

But what are we measuring if not growth, aesthetics? That can be measured but that's no longer a PLANT issue, this is a human perception/psychology issue.
And is reflected light vs absorbed light spectra driving the aesthetics?  That would also need to be controlled for.
And aquatic aquarium plant market simply is not worth much to research to answer most of such questions. 

There is likely something to the light spectra, but what it is etc, is a tough one to say, and then personal aesthetics are a huge issue.

Red/far red ratios play a larger role for allocations for many aquatic species. Aesthetics? No one has measured that in aquatic plant research to date I'm aware of.

I focus on reflective light, the nicer prettier reflected light, the better.
Like red plants? Add red lighting. Like red and blue colors? Add two colors of bulb types etc.
These are aesthetic concerns, not so much what is better. I get compact growth with low or higher light PAR, and the same with spectral types.

Colors? I get different colors with different bulb colors. That I am pretty sure about and would be willing to bet on, but it's not easy to test that either.
Now, I've finish the god awful degree, I'm working with a Biological supply company that produces some cool stuff and we should bring some products which you can dial in the anthrocyanin content(add more/less of the liquid etc).
This is independent of light. I can turn a green plant almost "purple". We are still a few months away.

Red spectra seems ignored by many, I welcome red colors, because they make the plants look better.


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## Tim Harrison

plantbrain said:


> One of the main questions and unknowns I've long had is can we design a wavelength set that will optimize the growth vs minimizing the energy input? PAR vs PUR.
> 
> There is likely something to the light spectra, but what it is etc, is a tough one to say, and then personal aesthetics are a huge issue.


 
I've been thinking the same of late...we have the technology and the methodology...and it would be interesting to quantify. I'm not doing much of any great interest at the moment so...if one of the industry biggies wants to fund the research I'll get right on it (CV available on request)


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## plantbrain

To what end though Troi?
Why don't biologist _always_ use PUR? 

The bulb brand and models will be specific and certainly be changed and marketed differently in a few years. 
You need the full spectral graph for PUR and this will change also.............as intensity goes up/down(plants will respond differently to both PUR and intensity). You you need to filter and change intensities over a wide range of variables.  
And this is just for one plant species!!!

You'd need to do 5-10 plants commonly kept in aquarium. 
That's a lot of work for very very little gain and you'd need a lot of space and equipment.

That is the trade off and why most Biologist simply use PAR, it does not answer such questions, but it's a heck of a lot easier to use and compare vs the full radiospectragraph.
Yes, we can answer many things, but the labor, changing products and technologies and effort to do so outweighs what we gain from it, since many horticulturist use sunlight, that's is what is most often tested, not fake light.

We can use something fairly weak like Lux or a camera meter, or use PAR or use PUR which becomes far more involved.
Lighting makers simply do not discuss any of this. 

Make take is to use PAR and then pick what you like personally.
Some observations amongst the hobbyists will be helpful and compre what everyone thinks based on consensus( a tall order for many hobbyists, but it's happened many times).


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## Tim Harrison

I'm sure you're right; I've read your discussion on this elsewhere. But it's an interesting concept nonetheless.


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