Reef Lighting Theory Basics

[Bombertech]

I grow tired of generalized blanket statements in regards to lighting technologies around here.  What should be a learning experience for all has turned into a fool’s errand where not enough information is presented in the attempt to mislead in the name of sales numbers.

 

So, to be helpful, I will do my best to explain some very important aspects of lighting specific to corals/fish.  My hope is that this will present a baseline of understanding from which we can all increase our knowledge of how we can best care for our small oceans in a box.  If this isn't for you, feel free to learn the following through trial and error

 

PAR:

 

PAR is measured as any wavelength between 400 and 700nm. Below is a graded chart for the Apogee PAR Meter.  In this hobby we use PAR as a light intensity unit of measure.  We use this versus lumens because lumens is weighted as the eye perceives it, not as a 1 for 1 comparison.  When we talk about PAR, it is in relation to a properly built/tuned lighting system that already takes in to acount some efficiency.

 

Correcting Chart for the Apogee PAR Meter

 

Lumens Chart

 

PUR/RQE:

 

PUR (Photosynthetically Useful Radiation) and RQE (Relative Quantum Efficiency) are nanometer by nanometer efficiency ratings used to determine how useful/efficient any given wavelength is for use in photosynthesis.

 

 

Zooxanthellae’s use of light:

 

Zooxanthellae has evolved to use the high UV-A/violet/blue/cyan range more efficiently as it penetrates water more easily.  Shallow water species can use the RQE peak (590-600nm Amber) more efficiently for photosynthesis as well as using this range for enhanced pigmentation (we’ll get to pigments/coloration a little bit later).

 

So, as you can see, the green and yellow wavelengths are not very efficient for growing corals if one was to use them outright.  However, we are not solely interested in growing corals, we strive for better coloration.  I could grow brown corals fast all day with a high PUR/RQE Fixture but if the proper wavelengths in adequate spectrum are not present, color will not be at its full potential.  Note the simularities between this chart and most spectral charts from reputable LED manufacturers.

 

 

 

Fluorescent Pigments:

 

Zooxanthellae are brown in appearance so the color we see are fluorescent and non-fluorescent pigments.  Fluorescent Pigments absorb a wavelength (this is called excitation) and re-emit light at a high wavelength.  This is called various things such as fluorescence, pop, color, etc.  The more light in the excitation wavelength, the brighter the color will be.  To make the color appear bright to our eyes, we try to balance lumens against the fluorescence of the corals to keep the color from being washed out by other light colors.  It’s interesting to note that there are no documented fluorescent pigments with an excitation above 600nm.  So orange/red does nothing for increased coloration in corals other than non-fluorescent pigments, most commonly seen in fish and a few red SPS species.  Red is efficient light for coral growth but it can lead to diminished coloration (browning out).

 

 

Kelvin Rating:

 

Kelvin Rating is used as an overall color indicator of the light, this is based on the emitted color of a black iron kettle if it was heated to a specific temperature.  Common kelvin ratings in aquaria are 10000K, 14000K, and 20000K.  As the kettle gets hotter, the light gets bluer.  However, since the overall color is the sum of light, there are numerous ways to get there.  Some manufacturers use blue and white diodes (cool/neutral/warm/other) to mix up to a desired kelvin rating.  Others opt for a more selective approach by using more specific wavelength diodes to maximize efficiency with both coloration and growth.

Spectrum:

 

UV-B/C:  UV is divided into 3 bands, UV-A, UV-B, and UV-C.  UV-C damages cells which can result in death to the organism, UV-B causes light damage but does not destroy cells instantaneously, UV-A is the least damaging of the UV types.  Corals have evolved to protect themselves from light damage by producing their own sunscreen in the form of fluorescent proteins. 

 

UV-A:  When 360-400NM are used, the corals adapt by increasing fluorescent pigments to convert the incoming color (UV) to something either usable for photosynthesis, or as a color that is less damaging.  These can be anything from violet/blue/green/yellow/red and develop slowly over time.  The outgoing wavelength is ALWAYS greater than the incoming.  Outgoing wavelength is based on the genetics of the coral and what proteins it has.  Now, think of the addition of UV-A like tanning.  The right amount increases color but too much can stress the coral.  What we have seen with the addition of UV-A is increased coloration.  The color depth is more pronounced, you start to develop nice fluorescent violets that were not present before as there was no light to excite them.  Growth increase a bit but not as much as the next band of light.  These diodes are specially made for autoclaves and other medical equipment, they are hella expensive and no one carries them.  Only a few light manufacturers use diodes that bleed into this range (The AI SOL Hydra 52’s for instance use 400nm peak diodes for this)

 

Violet:  401-439nm is violet.  People a lot of times call violet UV, it’s not and usually used in marketing.  Violet is very high in RQE/PUR specific to corals (generally speaking useful light for zooxanthellae peaks at 430NM).  This is where you get increased growth, and a lot of color.  Technically, you can grow corals just fine on this light alone.  If someone wanted to grow corals with the lowest amount of light, a fixture with just 420-430nm leds would be the most efficient light you could use.  I ran a single 100W test fixture of 420-450nm violet/royal blue over a 48x48 tank for two year, growth was great and coral color was pretty decent.

 

Royal Blue: 440-450nm: High efficiency, and good coral coloration. This is used quite a bit in the nicer commercial fixtures, however, since it adds a purple hue, the color will ultimately need balanced.  Various lower end fixtures will omit this spectrum for 470nm blue.

 

Blue: 460-480nm:  This is a bright blue, it excites colors and has decent photosynthetic efficiency.

 

Cyan: 490-510nm:  Cyan excites fluorescent pigments, is low/mid-range in photosynthetic efficiency, and gives a desirable hue to the water.

 

Green: 515-550nm: Green excites some fluorescent pigments, is low in PUR (gradient downwards the higher the wavelength gets), and high in lumens which can overpower other colors if we are not careful.

 

Lime: 566nm:  Lime is low in PUR but excites a lot of Yellow/Orange/Red Pigments.  It is also used for white balancing and increasing lumens.  MH/T5 usually have a parasitic peak at 560nm.

 

Amber: 690-600nm: Amber is low in PUR but excites a lot of Yellow/Orange/Red Pigments.  It is also used for white balancing and increasing lumens.

 

Orange/Red: 601-700nm: Red is used by chlorophyll A present in zooxanthellae with a peak efficiency (PUR) of 660nm.  HOWEVER, there are ZERO fluorescent proteins in this range.  So, you get growth, but it can “brown” the coral.  Commercial fixtures use a lot of red to make up for the lack of PUR on the violet/royal blue side but it comes at a heavy price to coloration.  This is where the age old “10-14K = fast growth, bad color, 20k = slow growth, good color” comes from.  BUT, there is an infinite amount of ways to mix color to get to 14/20K.  Red is also used for non-fluorescent red pigments (such as the red color on fish, and some corals).

 

White LED’s:  White LED’s should be used cautiously but a lot of times they are not.  Personally, I only use a couple to decrease pixelization between colors also known as CRI (color rendition index).  It is important to select the right white leds.  Cool white has a peak of blue which is fine, but also a lot of green and drops before it gets a lot of lime/amber (so you lose color potential overall but you can white balance with it).  Warm White has a peak at 620nm orange, but puts us into red.  This isn’t good for coloration, but is fine for growth.  Somewhere in the middle is a decent white, sometimes called neutral white:  for me, that means looking at each vendors spectrum graphs to find one that minimizes anything above 600nm, but doesn’t put us to far into the green spectrum.  These vary based on manufacturer and binning.  Custom whites (toted by some vendors) can be more efficient that the other white diodes but it really depends on what you are trying to do.  Personally, even the most highly acclaimed custom white diodes I’m seeing have a lot of waste spectrum you could eliminate by using different narrow band diodes.

But, that costs more money and would have to come out of the bottom line and take away from things like marketing.  A quality light at a fair price sells itself in my experience.  We are starting to see vendors drift away from the blue/white start we saw at the beginning of the LED evolution.

 

With this as a knowledge baseline we can discuss the pro’s/cons of various light systems.

 

-Matt (Bombertech)

 

 

[Bombertech]

Here is a RQE Multiplier table for those interested in calculating a light's photosynthesis efficiency.

 

[Emerald525]

Thanks for posting this. I will definitely follow along in this thread and read this thoroughly when I have time. Very nice summary!

[Bombertech]

Thanks for posting this. I will definitely follow along in this thread and read this thoroughly when I have time. Very nice summary!

You're welcome, I know there is a lot of information there [emoji33]

[TheClark]

I try to keep up on LED technology, but always learn stuff from bombertech.  Thanks Matt!

[Peng]

Just got out of pchem and look at this be like 

Useful info though. I'll follow this thread.

Edited March 19, 2015 by Peng

[sroberts]

Does the club still own a PAR meter that can be checked out?  I would love to measure my lighting that I am using.

[badxgillen]

This is all old news...Where is the PUR chart for the "Best most "Useful" LEDs, can you tell me that  ? 

 

There is some sarcasm in the end there, you don't have to answer that.

[Ninjabeaver]

This is all old news...Where is the PUR chart for the "Best most "Useful" LEDs, can you tell me that ?

 

There is some sarcasm in the end there, you don't have to answer that.

Anyone who is in the know would know that you have to spend at least 3000 to light your tank for the best PUR.

[Bombertech]

Yes, we do have a group PAR meter. You might ask Pledosophy how to get it.

[reefnjunkie]

I have to ask your thoughts on the PUR/PAR relationship.

 

I mentioned this back when I was trying to have an intelligent conversation with a certain individual that although a fixture may have, say, 100% PUR if it lacks PAR than PUR doesn't amount for anything.

 

Here is why I ask-I was given an AR light years ago to have and to review and to then post my findings. As some may not know the AR (Aqua Ray) has been touted as having 100% PUR 

 

Anyway the fixture did great in my 9" deep frag tank   as long as I stayed under a 10 square inch footprint directly under the light, get out side that 10" and corals faded and started to die (Im speaking acros). If I got 6" off the edge of the fixture PAR dropped to 60-80 but the par was 275 directly under that fixture that was hung ~ 6-8" above the water. Those are some pretty horrific numbers in my experience with LEDs

 

This brings me back to my point/question, and I come to making this statement from my experience in using a fixture with 100% PUR- PUR means nothing in regards to the ability to successfully keep and grow corals without having sufficient PAR.

 

AM I in the right ballpark

[pledosophy]

Thanks for doing all this Bomber. It's nice to have such knowledgable people in the club we can turn to for this kind of information. I know it helps me out, I'm sure it helps out many others. Fascinating stuff.

 

Yes, we do have a group PAR meter. You might ask Pledosophy how to get it.

Just sitting on my shelf at home. Any PNWMAS member can pay the deposit and check it out.

 

Anyone who is interested PM me.

[The ReefBox]

Hey Matt, so having the knowledge base you do. Could you rate the OR arctict247. Thus is not a dig at all. I turn 6 on my tank and would be curious where this light falls into the category. Is it good for growth, color how are wavelengths etc.

 

Thanks in advance

Brian

[Lexinverts]

Cool thread, Matt!

 

My comment is an aside, but the thing that really intrigues me about light and corals is the crazy fluorescent proteins and why they exist at all. Why did natural selection favor those disco-lights in our corals? Scientists have tested lots of hypotheses, but there is not really solid evidence for any of them yet. This article goes through some of them, and has some cool data on fluorescence in different species of coral if any are interested.

 

http://www.int-res.com/articles/meps_oa/m364p097.pdf

 

Here at OSU, there are several labs working on isolating new coral fluorescent proteins from corals for use in biomedical research.

 

In 2008, three researchers from Woods Hole won the Nobel Prize for first isolating green fluorescent protein from a jellyfish and making this type of research possible. Some day the we may owe finding the cure to Alzheimer's disease to fluorescent proteins.

 

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2008/popular-chemistryprize2008.pdf

Edited March 20, 2015 by Lexinverts

[Ninjabeaver]

Cool thread, Matt!

 

My comment is an aside, but the thing that really intrigues me about light and corals is the crazy fluorescent proteins and why they exist at all. Why did natural selection favor those disco-lights in our corals? Scientists have tested lots of hypotheses, but there is not really solid evidence for any of them yet. This article goes through some of them, and has some cool data on fluorescence in different species of coral if any are interested.

 

http://www.int-res.com/articles/meps_oa/m364p097.pdf

 

Here at OSU, there are several labs working on isolating new coral fluorescent proteins from corals for use in biomedical research.

 

In 2008, three researchers from Woods Hole won the Nobel Prize for first isolating green fluorescent protein from a jellyfish and making this type of research possible. Some day the we may owe finding the cure to Alzheimer's disease to fluorescent proteins.

 

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2008/popular-chemistryprize2008.pdf

Back in my college days i worked as a helper in the James Carrington lab building...washed a lot of pots and thinned out many tobacco plants. They were doing genetics stuff to make the plants fluorescent under UV light.

[Bombertech]

I have to ask your thoughts on the PUR/PAR relationship.

 

I mentioned this back when I was trying to have an intelligent conversation with a certain individual that although a fixture may have, say, 100% PUR if it lacks PAR than PUR doesn't amount for anything.

 

Here is why I ask-I was given an AR light years ago to have and to review and to then post my findings. As some may not know the AR (Aqua Ray) has been touted as having 100% PUR

 

Anyway the fixture did great in my 9" deep frag tank [emoji144] as long as I stayed under a 10 square inch footprint directly under the light, get out side that 10" and corals faded and started to die (Im speaking acros). If I got 6" off the edge of the fixture PAR dropped to 60-80 but the par was 275 directly under that fixture that was hung ~ 6-8" above the water. Those are some pretty horrific numbers in my experience with LEDs

 

This brings me back to my point/question, and I come to making this statement from my experience in using a fixture with 100% PUR- PUR means nothing in regards to the ability to successfully keep and grow corals without having sufficient PAR.

 

AM I in the right ballpark

PUR/RQE is going to be the percentage of PAR that is actually used for photosynthesis. So let's say a standard fixture has an RQE value of .75 overall, the super duper fixture has an RQE of 1.

 

At 300 PAR on the superduper fixture you would have the equivelent output of 400 PAR on the standard fixture. Most fixtures out right now use a majority of light that falls into the higher PUR/RQE wavelengths (450nm blue dominant peak) so generally you'll be looking at a 10-25% deviation.

 

Remember, none of that takes into consideration wavelengths used for increasing pigmentation. Personally, I'd gladly drop my efficiency to 50% if I'm using wavelengths for increasing color. When I say increased color, I'm talking about colors so bright they illuminate the fish as they swim past. If I wanted poo brown corals I'd be running solatubes over my tanks.

 

I know you know this but for everyone else, make sure to adjust your PAR reading, if you look at the PAR correction chart, if any light falls out of the receptive range Usually anything lower than blue, then go ahead and add the correction factor which for a 450nm peak is about 25%.

[Bombertech]

Thanks for doing all this Bomber. It's nice to have such knowledgable people in the club we can turn to for this kind of information. I know it helps me out, I'm sure it helps out many others. Fascinating stuff.

 

Just sitting on my shelf at home. Any PNWMAS member can pay the deposit and check it out.

 

Anyone who is interested PM me.

No prob! I'm always glad to share/help!

[Bombertech]

Cool thread, Matt!

 

My comment is an aside, but the thing that really intrigues me about light and corals is the crazy fluorescent proteins and why they exist at all. Why did natural selection favor those disco-lights in our corals? Scientists have tested lots of hypotheses, but there is not really solid evidence for any of them yet. This article goes through some of them, and has some cool data on fluorescence in different species of coral if any are interested.

 

http://www.int-res.com/articles/meps_oa/m364p097.pdf

 

Here at OSU, there are several labs working on isolating new coral fluorescent proteins from corals for use in biomedical research.

 

In 2008, three researchers from Woods Hole won the Nobel Prize for first isolating green fluorescent protein from a jellyfish and making this type of research possible. Some day the we may owe finding the cure to Alzheimer's disease to fluorescent proteins.

 

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2008/popular-chemistryprize2008.pdf

Thanks! What interests me most about the flourescent proteins is how they change/morph over time. For instance, I have some BTA's that have been receiving a lot of lower wavelength light for over a year via high intensity spot lights. Under black light they glow red, the other BTAs do not. It's amazing how they adapt.

[Bicyclebill]

Awesome write up Matt! Great info all condensed into one place.

[The ReefBox]

PUR/RQE is going to be the percentage of PAR that is actually used for photosynthesis. So let's say a standard fixture has an RQE value of .75 overall, the super duper fixture has an RQE of 1.

At 300 PAR on the superduper fixture you would have the equivelent output of 400 PAR on the standard fixture. Most fixtures out right now use a majority of light that falls into the higher PUR/RQE wavelengths (450nm blue dominant peak) so generally you'll be looking at a 10-25% deviation.

Remember, none of that takes into consideration wavelengths used for increasing pigmentation. Personally, I'd gladly drop my efficiency to 50% if I'm using wavelengths for increasing color. When I say increased color, I'm talking about colors so bright they illuminate the fish as they swim past. If I wanted poo brown corals I'd be running solatubes over my tanks.

I know you know this but for everyone else, make sure to adjust your PAR reading, if you look at the PAR correction chart, if any light falls out of the receptive range Usually anything lower than blue, then go ahead and add the correction factor which for a 450nm peak is about 25%.

Matt can you explain the correction topic a lil better. For example OR t247 users

[JManrow]

Dana Riddle has visited the Portland Marine aquarium club a couple of times before it became PNWMAS. He was explaining PAR to us back in the 1990s, but he also mentioned that what is needed was lighting actually recognized and utilized by marine organisms. I have known Dana for bout 20 years and I know he would be glad to visit Portland again as a speaker. I have spoken with him over the years and wanted to make sure there was enough interest in him giving a presentation. Let me know.  Here is an article written a few years ago. http://www.advancedaquarist.com/2007/10/review

Edited March 20, 2015 by JManrow

[softy]

as usual Matt.... great information, great write up.  Some day i will make it to Bend with a container full of corals and do some swapping...  eyeball your fixtures!!!  

[Bombertech]

Matt can you explain the correction topic a lil better. For example OR t247 users

Unfortunatly I don't have time today to run a nm by nm calculation of PUR/RQE, but to be honest, that information doesn't do anyone a whole lot of good without something to reference it against.  RQE is only a small piece of the puzzle, especially considering how similar reef lighting spectrums are these days.

 

To do a true apples to apples compairison you would be factoring diode efficiency (efficacy), power supply efficiency, dimmer efficiency, etc.

 

To help out I did run a quick spectral calc on the OR T247 since I have never seen one done.  One thing to note, the majority of users run their fixutres at approximately 100% Blue, 50% White so I ran the numbers to factor this data versus the industry standard of providing spectral information at 100%.

 

You can take this graph and compare it to the relative quantum efficency table provided in my second post if you want to.

 

[Bombertech]

Dana Riddle has visited the Portland Marine aquarium club a couple of times before it became PNWMAS. He was explaining PAR to us back in the 1990s, but he also mentioned that what is needed was lighting actually recognized and utilized by marine organisms. I have known Dana for bout 20 years and I know he would be glad to visit Portland again as a speaker. I have spoken with him over the years and wanted to make sure there was enough interest in him giving a presentation. Let me know.  Here is an article written a few years ago. http://www.advancedaquarist.com/2007/10/review

 

I for one would be very interested in a presentation/meet and greet.  The information outlined above is a great baseline for understanding the topic, informed discussion would be great for everyone   I think if our collective knowledge is at a decent level, it would free up time for some very interesting discussion on more specialized topics such as coral flourescence, pigment transfer, photo-inhibition, etc.

 

Oh, and thanks for the shout out to the Central Oregon Reefkeeping FB page on the PNWMAS meetings.  There are a few reefers over here I am trying to get to join.

[Bombertech]

Awesome write up Matt! Great info all condensed into one place.

Thanks, when i first started delving into lighting tech I had a hard time tracking down information, hopefully this helps streamline some of the basic information.

 

as usual Matt.... great information, great write up.  Some day i will make it to Bend with a container full of corals and do some swapping...  eyeball your fixtures!!!  

We'll get there!  Hopefully soon there will be a couple custom fixture options out in the wild.  Someone in the Portland area gets a really nice prototype next week, can't say who yet.