LED Lighting and Robust Algae
Note: I posted what you see below on another forum. It garnered little response. I suppose that can be understood as only a small percentage of that large audience is experimenting with ATF/S. So with approval from the moderators I am placing the topic here. I have edited out the few responses received and I will make adjustments as necessary for the purposes of clarity.
What I have written so far is more a stream of consciousness than any one specific thing. I'm trying to grasp this material and am hoping those more knowledgeable can shed light on some of these areas. It won't take much to exceed my range of knowledge. But I think there's alot to be learned on the topic.
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I have looked at more spectrum graphs and read more forum posts and browsed more published articles in the last few week than...
From what I have been able to cull from all this reading is that Chlorophyll A responds in the 430 and 660NM ranges and Chlorophyll B responds in the 455 and 640NM ranges. I have also noticed some references to carotenoids and their response in the 470 to 500 NM range.
So here are some observations/questions:
Much of what I have read on the various marine aquarium sites regarding LED's and turf scrubbers focused almost exclusively on the "deep red" range and the mention of light in the blue regions is thrown in as an "if you really want to". This addresses just the red end of chlorophyll A and pretty much ignores chlorophyll B. I can't say I've really run across any discussion regarding providing beneficial light spectrum for carotenoid development even though carotenoid seems quite beneficial to the overall health and vigor of these algae.
So, in general, does it really matter? What I mean is, does practical application show that specific light spectrum isn't as crucial as much of the published information lead you to believe?
My assumption is that the published articles on marine algae would be based upon some empirical evidence, i.e., someone tried growing algae with 630nm light and had poor results compared with 660nm. As I look at the spectral distributions on some of these diodes, the spread is about 15nm wide to -50% output point. Taking as an example the Cree XP-E- it has zero output in the 660nm range. Yet, the XP-E is marketed by well-regarded suppliers as an "algae scrubber diode".
Then, looking at warm-white fluorescents, their output in the red range peaks in the low-600 range, but noticeably, they all seem to have a big bump in the green range, in the low 500's. That's where the carotenoids live.
From all of this, I'm looking at some potential explanations...
--These algae will grow with just one of the three photosynthetic compounds supplied proper light.
--The above, but with only one of the two parts of the spectrum in their needs range (ex: Chlor. A, only 660nm/no 430nm.)
--These algae will grow with light close to but not exactly in their ideal spectral need range.
--Algae will grow if you shine a flashlight on it.
I kept reef tanks 20+ years ago. I'm returning to the hobby now- I figure if I can keep two kids alive long enough to graduate college I can probably keep a captive reef. But, I learned back then that success with a marine aquarium isn't keeping it going for a year, it's keeping it going for a decade. My concern is constructing something that will work OK but unbeknownst to me, is nothing more than a delayed catastrophic failure.
---- Then----
(In answer to a comment about a recent changeover from CFL to red/blue LED)
If you're using royal blue and 630 red, your algae shouldn't grow all that well. And to your comment about CFL's, if you were using one of the readily-available 2700k bulbs, most likely it had a very broad spectral band, including a good amount of green. Compare that to a blue/red setup which has two 15nm wide peaks in a 350 nm wide band of light. The CFL is maybe something that can be chalked up to intensity... Or maybe all CFL's aren't created equally- in fact, I know this to be true.
As I continue to read, I see a broad spectrum of successes and failures with ATS systems and most of the discussion is centered around water flow and food inputs. I'm beginning to wonder if the issue isn't two people with the identical setups having different results isn't because they don't really have identical setups. If you look at any of these color LED's, they're sold as, for example, royal blue advertised as 455nm. But out of a random batch, I could get a bin with as much as 25% light output and a spectral peak 25nm different than yours. So if the research I have read is to be believed, my new red LEDs might be putting out a light spectrum that's almost invisible to my algae and yours is in the exact needed spot. But we are both using the same LEDs.
This leads me to wonder about the people using CFL's and their relative successes and failures. CFL spectral curves are much more broad than an assemblage of color-specific LEDs. But even then, not all two are the same. Different manufacturers get to 2700K in different ways. Just as LED manufacturers do. Some neutral white LEDs have strong output in the red spectrum and some don't at all. But they're sold at the same color temperature and relative CRI.
I know LEDs hold the most promise for algae propagation. But is success or failure a matter of what got randomly grabbed out of a parts bin?
----Then----
The more I read, the better I am able to grasp just how little I know.
There seems to be a common assumption that chlorophyll is chlorophyll and it functions the same in each organism that it is contained in. That doesn't seem to be the case.
I have seen a number of light curves identifying the photoreactive light frequencies that certain chlorophylls react at. But there's another element- it's referred to as the action spectrum of photosynthesis. These are much broader curves, not the 15nm wide spikes shown in the previous charts.
A couple other elements are carotenoids and phytochrome. From what I am gathering, carotenoids provide some photosynthetic benefit plus also aid in protecting the algae from IR. Phytochromes are photoreactive in the far-red ranges. I'm just starting to attempt to understand their contributions. In short, the picture that I'm beginning to see is that you can grow algae in most light- I have read more than a few times how light-adaptive it is. But at the same time, provided optimal light, it grows much more strongly. Strong, health algae strips bad stuff out of the water more quickly and efficiently, and out-competes undesirable species on the growing substrate.
Some other things that I have been reading about are the effects of far-red light. This is from 660nm out to 760nm. Some of the literature I have read speaks to far red adding significantly to algae's co2 fixing and potassium uptake abilities.
Beyond that, I have come across some fairly new research coming from artificially-lighted agricultural applications where they have been supplementing far red into the end of the light cycle's photoperiod. The theory here being that this is one of the triggers that plants react to in order to compete for light. Exposure to this spectrum causes both enhanced growth and a stronger root system. This very much goes against the prevailing notion that it's just a plant and it's Ok to just flip the lights off. By the way, this is coming from a USDA funded initiative to investigate the application of LED's in artificially lit agriculture.
I think another observation from all of this is that once the lights go out, the algae goes to sleep. CO2 fixation and potassium uptake drops to a small percentage of daylight processing quantities. This alone has me questioning having only one algae panel instead of two operating on opposite schedules.
The rub is that the majority of legitimate scientific research is aimed at wastewater treatment, biofuel aqua-crops and towards the elimination of "problem algae". I have found nothing much beyond the marketing information generated by light manufacturers selling to the reefkeeping hobby. All of what i have seen there is very non-specific. Even in the legitimate research, there are broad variances in light requirements between closely related algae species. Some light a decent dose of green light. Some like blue down in the 430nm region.
I think what we are confronted with is a particular limitation in available LEDs. 20-some years ago (or so) the solution we all believed to be ideal was metal halide lighting. Aside from their inherent shortcomings of power consumption, heat output and short lifespan, they do present a one-size-fits-all light spectrum. LED's just don't work the same way. If you look at the spectral distribution of any high-CRI diode, it looks nothing like the MH.
If you look at the breakdowns of commercially available lights over on ledgroupbuy.com, it's apparent that the commercial manufacturers are using the throw the kitchen sink approach at the issue. If you have one of everything, it must be OK, right? In essence they're mimicking the MH spectrum. But some of this research shows that might not be the best approach, especially when you're talking about implementing far red.
On this next one I am very far outside my range, but the dope-grower guys are using far-red supplement in various fashions to first inhibit and then trigger flowering. I have so little knowledge of botany, I have no idea if there's any sort of analog here. Does hair algae flower? I sure can't answer that.
----Then----
I first found the USDA reference here-
http://www.actahort.org/chronica/pdf/ch5201.pdf
and from there googled until I got to here-
http://leds.hrt.msu.edu/assets/Uploa...ation-2011.pdf
which led me to here-
http://leds.hrt.msu.edu/publications/
which appears to be a treasure trove of LED research into horticultural applications, that I have yet to delve into. It's not easy when you have to look up the definition of every third word and once a paragraph you have to look up a basic biology concept that they didn't teach much about in engineering school.
As far as the MH usage, I like to think of that as "the American Approach". If a little works, use more. If you only need a small segment of the overall, don't sweat it. Huge energy usage and heat byproduct we have to refrigerate away? To hell with it- just turn the knob to eleven. Wait, that sounds like the way I've done just about everything since childhood.
With all due respect to the people in the aquarium biz who are selling LED solutions, what they are putting forth is a consumer product. They may love the hobby, but it's a business pursuit. Thus, what they're selling is a dot somewhere on a 3-D matrix of considerations of cost, manufacturability and product performance. What they're selling isn't, and doesn't have to be, perfect. It just has to work to some degree that enough people will purchase it in a quantity large enough to sustain their enterprise. It will improve as competition pressures each supplier to refine their product. I sincerely doubt that any one of them has done anything more than what I have begun to do. There's tons of research out there on light spectrum effect on photosynthesis, the origins of which are well over a hundred years old. Some of the best research was done in the 60's and 70's and just now is being expanded upon and researched in more depth. I would surmise there are two reasons for this. First, the art and science of LED's has recently progressed by an incredible amount. And in the last 4-5 years, energy costs have skyrocketed (thanks Barry!). I couldn't fathom that there's an aquarium grow light manufacturer out there that has done extensive (or any) action spectrum research with multiple algae and multiple spectral curve experiments. If there was, you would see this front and center in their marketing materials. Instead you see "Our proprietary blend of LED light spectrae coupled with our state-of-the-art technology..." Who can blame them? The market right now is soooooo tiny.
In ten years we will all be laughing about the primitive approaches we are cobbling together right now. I have a flashlight in the door of my truck that is literally brighter than the HID headlights on my car. It's no larger than a D-cell flashlight. It exists not because there's a market for flashlights like that. It exists because each and every one of those display lights in every store in the mall uses 80% of the energy consumed to generate heat. The technology just trickled down. And quickly. Once the horticulture industry likes what they see, LED manufacturers will be tripping over each other scrambling to provide diodes to the fixture manufacturers. And then there will be a lobby pushing for tax credits for energy-saving technology adaptation. And that's commercial viability. Interestingly enough, that LED is a possibility right now. There are companies that compound specialty phosphors and others that specialize in specialty diode production. All you need is a spectral curve and the $$ for an order.
I hope all this stimulates someone with more knowledge and understanding of the topic than I (not a high barrier) to weigh in and share some of that knowledge- if even on some of the biological basics. There's more than enough research out there on light and plant growth. What I'm hoping is that there's someone with a level of understanding that can offer guidance on the potential parallels between growing cucumbers in a cave and growing nuisance hair algae in a small box inside a dark cabinet.
One other quick comment about emerging light technologies- The average greenhouse operator cares about what's in the light fixture above his crops as the average reef-keeper cares about what's in the fixture keeping his corals alive. They just want it to work. That's why alot of these "white papers" don't get into the specifics. The USDA funded research as well as published stuff from grad programs really does contain a remarkable amount of specifics. The key is transferring this to our particular species of desired algae.
Frankly, I think if I could spend $3-400 on a proven fixture, I wouldn't have begun any of this. But I see the same approaches working in one place and failing in another, the light element intrigues me and I have a suspicion that the key to success in an ATF lies in a large part somewhere in that neighborhood.
25-some years ago I tried macroalgae filtration system with very good initial success and then catastrophic failure. Being pre-Google, the resources I had were incredibly limited. It amounted to guessing what Dr. Adey did and what a very thinly populated public library provided. I liked the concept then and I still do. There's nothing more appealing than a completely natural process.
Another good read.
http://hortsci.ashspublications.org/...rint/43/7/1951
Somewhere in the back of my mind, I recall reading about algae being biologically similar to various leaf lettuce varieties. This article addresses lettuce and also discusses white light.
"Many previous studies indicate that even
with blue light added to red LEDs, plant
growth is still better under white light."
The article also addresses some successes using supplemental green spectrum lighting. And while it doesn't refer to it directly, green is the section of the photoresponse curve that carotenoids react to.
I did notice that one of the authors is one of the individuals involved with one of NASA's ISS experiments using LED's in grow light experiments. i have yet to run across anything published on that initiative.
