Welcome to CleanTick - Network with thousands of cleantech researchers and experts - Join CleanTick >>

Correct LEd spectrum for growing Algae

I have done much research online into determining the ideal spectrum for growing algae.  My goal is to custom-tune an LED fixture for maximum algae growth and maximum filtration capacity.  So far, I have not been able to verify whether Algae best utilizes the Chlorophyll A or B spectrums, or a combination of both.

I build algae scrubber for freshwater and marine aquariums.  The algae is grown on a vertical substrate with the system water constantly cascading over it, and illuminated on both sides.  So far, the vast majority of people grow the algae with low-kelvin (2700-3500K) CFL or T5HO with great success.  LED builds have been all over the board, but some evidence suggest that algae (at least, marine algae) responds best to 660nm “deep red”.  Thus the limited data would seem to indicate that marine algae (green hair algae, in specific) absorbs mainly the Chlorophyll “A” specturn.

Adversely, the horticulture industry reports that plants respond much better to the equivalent wattage (input) of 630nm.  Growth of plants under 630s far exceeds growth under 660s.  The theoretical explanation is that 630nm LEDs output 3x the power of 660nm LEDs, and that the difference is mainly the result of intensity trumping spectrum.

The “A” finding is also compounded by the apparent total lack of algae growth under warm white LEDs supplemented with 455/460nm LEDs (“B” peak in Blue).  The lack of correct red component may be partially to blame, so this is only anecdotal.

I am currently preparing to run an experiment with 2 separate fixtures, one tuned to the “A” spectrum, and another tuned to the “B” spectrum.  The experiment will be performed on 2 separate uninhabited saltwater system with fertilizer mixed in the water, essentially creating waste water or runoff water.

I would greatly appreciate any insight from anyone who has attempted to grow algae using artificial LED light.  I posted a similar request on Oilgae and got zippo for response.


Answer this question Add to Reference Share Ask your friend to Answer

Login to share your answers / share a link - Login

12 Answers

  1. yankeeingenuity 5 years ago #

    This answer is oversimplistic but may help you. In short the answer is both Chlorophyll A and B. Where A has absorbs around 420nm and B at 680nm. A and B have a symbiotic relationship so it is wise to use blue and red and know the absorprion cooefficients of the species so you do not get the wrong LED. In general Chlorophyll B has 1/3 the "receptors" that A does so people suggest using 3x as many red. However relatively speaking 420-450nm is much shorter of a wavelength and therfore will no absorb as deep giving the same density and motion. By nature is scatters more. So intensities of bLue should be higher and adjust to exposure time. Hope this small piece helps. I would like to see a photobiologist provide an analysis of a popular culture here since this is gaining importance in closed PBR's.

  2. yankeeingenuity 5 years ago #

    To Budc ...I thought I was trying to basically answer your question but it looks like it came out like a statement. Have not used the site for a long time. Much is known about this topic and it would be really good if a photobiologist or somebody working in this area could provide some data as we know larger enttites have very exacting data on this. How did the test go?

  3. budc 5 years ago #

    yankeeingenuity, thanks for the response but I believe you are mistaken on a few things. Each chlorophyll type, A and B, has a red and blue adsorption peak. A is around 430 (blue/violet) and 660 (deep red) while B is around 460 (blue) and 630 (red).

    Also the comment on blue not penetrating as deep doesn't seem to make sense to me. In the ocean, for anyone that has been SCUBA diving, the blue light penetrates the deepest, the reds get washed out quickly. When you get much below 60ft everything starts to look blue until you turn a dive light on, then the colors burst. Also from many other discussions I've had regarding lighting in general, blue light has a much higher intensity/energy level and thus it penetrates deeper.

    I have not had much time to do my tests, but many others have been using varioud DIY builds as well as a cheap chinese fixture (that contains an array of 1W leds, 45 60nm reds and 5 455nm blues) and pretty much everyone has been using 660 reds instead of 630 reds, and have been getting great results (beating the pants off CFL and T5HO while running less "on" time per day).

    The "B has 1/3 the receptors" is particularly interesting. Are you talking about the red peak of "B" versus the red peak of "A" or are you talking about the red vs blue peaks?

    One other interesting result that someone posted was that they were running a scrubber with an array of 6 3W 660 reds for about 6 months, and when they added one 455 blue LED to the mix, the growth changed dramatically, not so much in bulk but in form; the algae 'roots' where it was attached to the screen/substrate became substantially stronger (harder to scrape the algae off) and the algae strands thenselves became thicker. This suggests that the blue component does not so much contribute to overall growth as it does to some other strengthening factor.

  4. yankeeingenuity 5 years ago #

    Hi Budc, How are things. wrote that 1st line wrong...sorry..the absorption spectra peaks for both A and B are well known in green algae. These are the primary photoacceptors (or photosynthetic units PSU's) in the choloroplasts. 660nm NIR and 440nm UV are very highly absorbed and in basic sense will reach saturation point very fast if the algae is not mixing resulting in self shading or light starved algae. I am assuming you are mixing. 440nm is a shorter wavelength and therefore scatters more in a culture medium than 660nm. Its really how many photons in a PSU area can be ultilized and how to attunate the light to get proper filling and discharge of photons.

    I was talking about B not the peak of B. I have not heard a full description of the relationship between these LHP's and how they affect growth rate and/or lipid content etc. They are there for a reason that is for sure. Any thoughts?

    BTW: Do you know of a good source to get LED's in a strip? Enviormental Sciences has them but they are very expensive. Thanks in advance.

  5. budc 5 years ago #

    When you talk about algae mixing and light scattering, is this coming from a background of growing algae suspended in a liquid? This is what I see on most of the pages I've seen for growing algae for bio fuel or some other purpose. Re-read my OP, this is for a mat of algae grown for the purposes of aquarium filtration, the substrate is vertical screen with a about 35 GPH of flow per linear inch of screen, and the screen is lit on both sides. So essentially there is a continuous sheet of water that is about 1/4" in "depth" cascading across the algae. Therefore light penetration and scattering IMO really does not apply, when the algae mat grows thick sometimes there is very little water over the top of the algae as the water flows through it. Since I'm growing green hair algae, I don't know if "mixing" applies.

    However I am interested in the saturation point. From what myself and others have experienced, this saturation point occurs when there is not enough nutrients w/r to the amount of light provided, and then the growth turns to a yellow, rubbery type of algae. Cutting the hours of the light back prevents this. Recent builds using 660nm LEDs have revealed that much less "on" time is needed.

  6. rcollins 5 years ago #

    Here is a link to chlorophyll A&B light absorption sepctrum.


  7. budc 5 years ago #

    Yeah, I've seen that graph in dozens of form hundreds of times. But I have yet to actually hear from anyone outside of the reef / aquarium forums that is trying to grow algae with LEDs. Anyone?

  8. rcollins 5 years ago #

    It is my understanding that the A chlorophill sectrum is for when the light is most intense (mid day) and the B chlorophill sectrum is for when the light levels are lower (in the morning and the evening where the A spectrum is filtered out by the atmosphere, because of the changing angles the sunlight hitts the earth).

    I believe this is so the algae can absorb the most amount of energy from the sun troughout the day. The graph also shows that the both chlorophill A&B absorb the light at both ends of the light spectrum.

    Deductive reasoning suggests that both red and blue leds need to be used at the same time, and the A spectrum would work the best, as long as the light isn't too intense (too much wattage).

  9. budc 5 years ago #

    Ok now that's what I'm talking about. That's a good tidbit of info. If that is true (about the sun cycle and atmosphere) then that is the best explanation of A vs B I've heard yet.

    There have been many people that have been running algae scrubbers using only 660nm, and some using 660nm with a blue 455 thrown in. What would be really interesting to see is if simulating the sun cycle would give an added boost. Say start out with the 435/660s on, then switch over to the 455/630s, then back. Or one where mid-cycle they're both on.

  10. rcollins 5 years ago #

    Just to add to my point, if you watch the sun come up in the morning, or go down in the evening, the light you see is kind of a redish yellow blue, and in mid day it is white. I haven't done a spectral analysis, but if someone did I think they would most likely come up with the same results, less far red, and less far blue in the morning and evening.

  11. budc 5 years ago #

    Oops yeah then that would be reverse of what I posted: 455/630 on the ends, 425/660 in the middle...

  12. johann 5 years ago #

    At Hort Americas we work with GreenPower LED products. One product which has captured the attention of algae research at the University of Kentucky is our Deep Red/ Blue Production Module. They have been very impressed with its performance on algae production. Contact me if you wish to know more.



Search Questions


20 Things You Can Do @ CleanTick

20 Things @ CleanTick