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PUR or RQE, YouTube Video Fail- Guide to lighting a planted tank

Updated 7/12/23

Here we have a YouTube Video titled: "Advanced guide to lighting a planted tank - Basics first"
https://www.youtube.com/watch?v=jKHwDfv6ETg

In this video this person uses my charts and states I am misinterpreting information, but what it really comes down to is he really does not like my terminology such as "useful light energy". Admittedly this is not scientific terminology, but I have been using this terminology to help my aquarium design clients understand in simpler terms concepts about lighting.

I should also note that I have been professionally employed in this industry since 1978 (longer counting as a hobbyist). During this time I have consulted, read, researched and has much time in hands on experience and experiments. Does this mean I am infallible? OF COURSE NOT!!
That is why my body of work has been and continues to be updated as new information comes along or I do find errors in my work, which I have.
Of these two lighting article he attacks, the "Aquarium Lighting Information" article has its roots going back to the early 1980s and has been on the Internet since 2005, long before LED lights were popular or even viable.

Here are the two articles in question:

*Aquarium Lighting; Guide to Complete Facts & Information
*PUR/PAS vs PAR in Aquarium Reef/Planted Lighting; LED Wavelengths

Right off the bat the author states that only light visible to the human eye can be used for photosynthesis, this has been found to be incorrect.
"Johnson et al. (1996) examined effects of infrared (IR) LEDs of 880 nm and 935 nm on etiolated oat seedlings. Spectroradiometric analysis of those long-wavelength sources showed that actual peak emission wavelengths averaged 916 nm and 958 nm, respectively. Compared with dark-grown controls, seedlings grown with 880 (916)-nm LEDs had shorter overall length but more advanced leaf emergence than either dark- or 935 (958)-nm-grown seedlings." From this reference: Plant Productivity in Response to LED Lighting

Next, the video author mistakenly misapplies the chart for PAS (Photosynthetic Action Spectrum) which is in fact quoted from Wikipedia, even though in private messages he advises us to read Wikipedia.
I will however admit that the chart was poorly located so as to give the impression that the PAS chart was intended to imply that any light outside it was totally useless, so the chart has been relocated. I will also admit that wording in other areas of the article did imply that green is totally useless (based on other textbook sources too) which has since been corrected, so on this point I think he was half right/correct.

However, this aside, the wording that was quoted from Wikipedia still stands, now with a quick link for lazy individuals such as himself to find easier in the reference section. Maybe now he needs to make a video correcting Wikipedia??

Below is the chart he misquotes:

Next, he infers that we state that green light is totally useless, when in fact we only stated it is not within the ESTABLISHED" action spectrum and that green light is less efficient and more importantly can slow growth of plants as per studies well beyond the "test tube" as he states. I know this from my decades of experience in experiments which includes use of fluorescent lights of different spectrums, including those with higher green and yellow content.

Next he states that most of the scientific community is in agreement as to plant use of green light.
Again, sorry Pal, I have been in this industry a long time and most text books (long before the Internet) as well as the accepted view WAS "Chlorophyll A absorbs its energy from the Violet-Blue and Reddish orange-Red wavelengths, and little from the intermediate (Green-Yellow-Orange) wavelengths".
Frankly, even the source he shows in the video is more theoretical as I discuss in my "PUR/PAS vs PAR in Aquarium Reef/Planted Lighting" using quotes directly from the source he cites!!
Here is an admittedly older .edu source, that was the commonly held view for years:
http://www2.estrellamountain.edu/faculty/farabee/BIOBK/BioBookPS.html

From the above cited .edu article:
"Chlorophyll, the green pigment common to all photosynthetic cells, absorbs all wavelengths of visible light EXCEPT green"
AND "Chlorophyll a absorbs its energy from the Violet-Blue and Reddish orange-Red wavelengths, and little from the intermediate (Green-Yellow-Orange) wavelengths"

I will however admit, that newer studies show that green light is only less efficient (up to 30% less efficient) and sometimes helpful other than just for "looks", however these same studies also show green light to be detrimental to growth in amounts higher than 25% of the overall light.
Reference: Plant Productivity in Response to LED Lighting

This all said, there IS a reason plants are most often green and that while plants can utilize green light, this is NOT the most efficient light spectrum. Even a recent PBS documentary stated this as a fact (I believe Nova, but maybe Nature, I unfortunately did not document the show). So for author of this video to attempt to discredit all this shows a disrespect for good science and science history, as well as a disrespect for others such as myself!!

We can document this efficiency quite easily with simple math, by simply taking the input energy in wattage to the output energy as measured by PAR at 400 mm in air (water has too many variables).
Even within the same product line, where everything is the same BUT the PUR and light spectrums, we can see a difference.
Then when other factors that differ among brands such as fans and lack of PWM use, the differences can be great.

EXAMPLES:
*AAP AquaRay Reef White NP 2000. This is rated at 30 watts input energy with a PAR of 380 at 400mm of air. This comes to .08 watt of input energy per 1 PAR
*AAP AquaRay Reef White 600. This is rated at 12 watts input energy with a PAR of 48 at 400mm of air. This comes to .25 watt of input energy per 1 PAR
*AAP AquaRay Fiji Blue 600. This is rated at 12 watts input energy with a PAR of 38 at 400mm of air. This comes to .32 watt of input energy per 1 PAR
*SB Reef Light PRO 32. This is rated at 363 watts input energy with a PAR of approximately 881 (100%) at 400mm of air. This comes to .41 watt of input energy per 1 PAR.

This clearly shows that the AAP/TMC AquaRay Reef White NP 2000 is the most efficienct aquarium LED light when sceince/math is applied (not just opinions)

Resource: AAP Premium LED Aquarium Lighting; AquaRay
AAP/TMC AquaRay Reef White NP 2000

Next he discusses the McCree Curve of 1972.
I think he either misapplies or thinks I do not understand this what is stated.
As for my understanding, let me be clear, while I have come to understand where green light can be more useful (hey I simply followed other text books and have learned better), with my strong science background including my knowledge of using radio waves for navigation as a pilot I certainly understand the basics of light energy.
For one, a photon is a photon, you simply have more energetic photons due to higher frequency. These higher frequency photons can penetrate water and even plant and even our bodies better (think X-rays). So a blue light of 480nm is going to penetrate deeper than a 680 red light wave, HOWEVER, they are both still photons!

Next, am I saying that photons of certain lights are better than others? No, again a photon is still a photon. However if light A has a PAR of 100 and light B also has a PAR of 100, but light B has its photons with frequency levels or are more energetic or less energetic in to such a frequency that is more efficient for specific aspects of photosynthesis, then the answer is example B is the better fixture even with an equal number of light photons.

Reference: Accuracy of Quantum Sensors Measuring Yield Photon Flux and Photosynthetic Photon Flux

Interestingly he displays a picture showing how NASA uses red light to grow plants in space, but where is the green and other middle colors?? No one argues aesthetics, or even that green light can be utilized (just less efficiently) which is why I never once advocate using just red and blue lights over ANY aquarium.
This is exactly the point I make in both articles that red and blue are more efficient, I also provide links to vertical farms to proves this point. Interesting that he attacks me, then makes my point!!!

He next correctly states the excepted range of PAR is 400nm to 700nm, however some recent science has also shown using infrared (IR) LEDs of 880 nm and 935 nm on etiolated oat seedlings showed leaf emergence, so these parameters may someday need better defining.
I reference this in my Lighting Article; PAR Section

I would disagree with the YouTube video author as to how well a PAR meter measures the light within the 400-700nm range, as it has already been established that these meters are by much more accurate in the middle yellow/green spectrums. This is documented just within one product line where everything is constant including wattage input energy, yet the PAR of a more blue fixture is 38 while the daylight fixture is 61 µMolm. This is a key point that many such as this YouTube author miss.

He next discusses Kelvin and I will agree that the YouTube author does an excellent job of describing Kelvin, going into more depth than my Aquarium Lighting article as to this subject (although outside this video, he miss-applies Kelvin ratings, more later in this article).

His next commentary states that quality of light does not matter.
WHAT?
There is so much evidence to the contrary but I think he is simply confusing terms such as the concentration of photons since he clearly is a very knowledgeable person.
Taking this statement to its logical conclusion, why not then utilize UV-C light, as the wavelength of a UVC blue photons is lower yet with higher frequency and even more energy. We know of course that this is not true and would actually be damaging to plants and most certainly livestock in the aquarium (as well since no UVC reaches the Earth's surface, no photosynthetic plant could have evolved to utilize it).
He even contradicts himself here with this comment since PAR describes the primary spectrum of useable light energy needed by plants. As well he even states that green light is less efficient.

Now I am not saying he does not understand what he is talking about, only his explanation. Frankly I had to listen to this several times to realize he is over simplifying within the PAR numbers. My guess is he simply is misapplying the McCree curve as to reflection of green light, missing that even of the green light that is NOT reflected, it is still often much less efficient (although there are synergistic applications where green when used in a small percentage improves growth too).
However just as he does not appear to like my simplification using terms such as "useful light energy", to which I would agree that it too can be taken as an over simplification, his comment in this video can be taken in a totally false manner.

To the left is a picture from an experiment that I happened upon around 2007 that really made me start looking into and watching LED light more.
In this picture, the 12 watt LED CLEARLY outperformed the 175 Watt Metal Halide. This is a CLEAR case of quality over quantity as there clearly is a QUALITY of light, and and his statement to the contrary is demonstratively wrong!

This is also a selling point of most LED brands over other lighting sources. There are also many other examples that I cite throughout my articles, as well as simply practical experience such as my experiments with different fluorescent light sources that scream out that this is an incorrect statement!!
How this author can make this comment or misstatement, yet attack me for disagreement of terms is mind boggling.

What is also interesting is the author is using 2700k philips warm white CFLs and claims his favorite light now is a 3000k LED. These lights are well outside his favored RQE McCree Curve, more importantly experiments I conducted as far back as the 1970s using fluorescent warm white lights showed that much more input energy (joules) were needed to obtain plant growth. As well, only when actinic blue (420nm) was introduced to balance out the warm white, did growth rates increase (again recent research bears this out too).

Reference: Real World Application of RQE, PAR. PUR, PAS, & Photons

EDIT AS PER KELVIN/6500K LAMPS

The video author has later displayed a picture showing four different lamps, claiming all are 6500K lamps when in fact the two on the top are clearly not (the third one down is an Ultra Sun by ZooMed which is in fact a 6500K and looks it as well).
While I would not argue that Kelvin ratings are not always accurate predictors of light spectrums/nanometers, these Kelvin ratings are also NOT this far off either.
This post actually does a good job of showing that while he might be well educated in modern lighting, he clearly has no knowledge whatsoever of lighting history (since he is relatively new to the hobby).

Whether he made this error on purpose or simply fell for an incorrect kelvin rating is not for me to judge, HOWEVER I CAN STATE FACTUALLY THAT ANYONE WITH EVEN REMEDIAL LIGHTING HISTORY KNOWLEDGE THAT THE ONE LAMP THAT IS QUITE PINK IS CLEARLY AN AQUARILUX KNOCK OFF!!
The Aquarilux is a popular lamp used to provide color for aquariums back in the 1970s, 80s, and into the 90s. It was NOT marketed as a 6500K or planted aquarium lamp and did NOT perform as well as those that were such as the Trichromatic or Tritons!

The author has also stated elsewhere that Kelvin is irrelevant since it is based on a black body radiator. HOWEVER, while our coral and plants are not black body radiators, THIS IS IRRELEVANT since Kelvin in our usage is simply a predictor of light spectrums.

Further Reading: Aquarium Lighting; Kelvin

~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I have a co-worker who even had a discussion with the author of this video and he displays the typical logical fallacy arguments of so many by getting personal in attacks and simply dismissing good documented outside research when he cannot or refuses to debate the known facts and professional observations that are well established.

Here are some followed by my comments:

Dennis W. 1 day ago
Since you have failed to 1. Demonstrate better quality of science references 2. Demonstrate actually growing better tanks (unlike say ADA or this channel). There is really no point in taking you seriously. This will be my last reply. The answers are in the papers listed above. Or even wikipedia has more accurate interpretations of the charts used in the site you listed.

Devon T. 1 day ago
1. I provided sources, you're ignoring them. 2. What would growing better look like? I have to proof myself by having "better looking growth". You failed to take a look at the references didn't you? You never got me my snips of what you think is important from the article, but I knew you wouldn't... Green is used, but there's no reason to focus on it. I don't believe anyone is saying green is useless, just that it's more of a useless energy. Green is used but it's more useless when considering which colors are required for photosynthesis. White lights will give you enough green and if there's added greens in a fixtures, it's cause the manufacturer has done a poor job a selecting the right white, which has the blue, green, and red. This is the idea of PUR, which I think you're disagreeing with me about. If you want a real world example: Here's a university level study, which measured growth when using MH & VHO, then switched to LED emitters which focused on blue and red, with less green and yellow. There was an extreme difference in growth.
St. Mary's College of Maryland Marine Biology LED Experiment
Yes, we don't not need to continue this discussion. I find my experience chatting with you to be somewhat disrespectful and insulting.

Dennis W. 1 day ago
**Your source is amateurish to be honest. It's not even a published paper is it?*** It's just a blog. on corals rather than plants unlike the links in this channel. Linked to your own site no less lol. I do agree with the point on blue, green, red though - always have. There are still errors on the pond answer and american aquarium products site, ***where you misquote the McCree curve for that of a PAR meter. TBH, a few of your friends asked me to ignore you completely.*** But I don't think you're malicious, just another site with ***over-arching claims on PUR - which is relatively unstudied specially on aquatic plant species (corals don't count)***. Until better studies arise, closest studies of terrestrial plants show what this vid talks about. (details in the many papers)

Devon T. 1 day ago
+Dennis W. Seems you can't stay away and you're not a man of his word.... Yes, the blog is current and is following the study as it's happening. It's meant to be an "amateurish" site to follow a university study. Again disrespectful. Never stick to the fact, you go personal. You're acting like I (or the author) invented PUR. There's graphs on the PUR vs PAR article, which clearly shows what greens Photo Efficiency is. I'm not even sure what your problem with green is anymore, expect that you said "all these sites and forums" are calling it useless. I don't see that to be the case. As far as it's efficiency, yea it's pretty useless, but is used and does provided benefits. It can also be detrimental with too much of it. I think what part of the problem is... it's almost like you're picking and choosing what to read. I'm having a hard time finding anywhere where someone is staying green is useless. This was an "old school" train of thought. You're welcome to pull points and quote them as to what you think is incorrect.... Instead you get personal and disrespectful.
Somewhat childish. TBH. You dont know my friends. To me, you're just another hater of PUR, as if you know something others dont. As like what was said in your video was something new. If you and others stop looking at PUR as just what light is being provided to a tank, you might get to understand what PUR can do for an overall aquarium LED. This is a huge oversight and limiting thinking for this hobby. The hobby will not continue to progress with this attitude.

MY COMMENTS:

He finally actually reads one source, but only briefly and once again gets personal calling it "amateurish" when in fact this blog simply makes it easy for the average reader to follow a well respected pHd scientist at St. Mary's College of Maryland.

Reference:

St Mary’s Marine Biology LED Experiments

However Dennis did find an error in our comparison of the PAR meter to RQE, but unlike this person, we constantly update all our articles, including when we are wrong, so this was removed.

In Conclusion;
One has to guess that this person is hiding the fact he works for a well known manufacturer based on his comments and blog posts forwarded to me.
It is interesting that he goes after my terms of useful energy that I have been using for decades but misses a popular manufacturers website which totally misapplies the terminology for PAR that more applies to PUR, more using word "needed" light energy instead of the more correct term used by Wikipedia of "able to use" light energy

What is also noteworthy that while all I have done here is defend my work, which I will be the first to admit that I have had to make corrections. But then we are all learning and the difference in my articles and most others and videos is that my content is constantly evolving as I learn more or even due to corrections.
This video author on the other hand has attacked me in personal ways in many forums (which I have not even addressed here) and does not have the humility to realize maybe he might make mistakes too and learn from others as I have, especially those who have considerably time in the industry.

Reference:
Photosynthetically active radiation (PAR); Wikipedia