DIY LED Fixture for growing chaeto (macro algae)

[Boga]

Maybe some of you know, maybe you already researched it. What kind of LED's in terms of spectrum are best for growing chaeto?

Are the warm whites better? What about the red ones or green? A mix between them?

Thank you.

 

[KBennett]

I'd imagine warm white is best.  Green would be no good.  Algae is green because it reflects that colour rather than absorbing it.

 

[Victoss]

I think when people make LEDs for algae they generally go with reds and warm whites.

 

[Boga]

.... Green would be no good.  Algae is green because it reflects that colour rather than absorbing it.

Makes perfect sense to me. Extrapolating from this, can we assume that red light will promote green algae but will not promote growth of red algae and red cyanobacteria?

I think when people make LEDs for algae they generally go with reds and warm whites.

Thanks KBennet and Victoss. I assume chaeto is a surface algae, shallow waters, where sun light is not filtered towards blue spectrum.

 

[Boga]

Interesting information on this link: http://www.thefragtank.ca/forum/index.php?topic=32.0

Some organisms, such as Cyanobacteria, purple bacteria and Heliobacteria, can utilize light in regions such as the low infrared. These bacteria make use of the unusable light discarded by the plant kingdom, in this case, light outside the PAR range required by plants, which is why Cyanobacteria thrive in lighting conditions that include the more yellow 4000 K and below and why actinic (50,000K) as well as balanced light in the 6400 to 14,000K range combined with passing water through an ultra violet sterilizer (to kill free floating Cyanobacteria) is important for control.

In the case of Red Slime Cyanobacteria, these Cyanobacteria do not use the PAR spikes at 435nm and 675nm and instead utilize more of the middle yellow and green light spectrum that is most common fluorescent (even so-called aquarium fluorescent lights) and incandescent lighting.

After little bit of looking around, it appears that the optimum for chaeto is a mix between deep reds and royal blues. I will post more data.

 

[Boga]

I will try to explain little bit why I think Red and Blue LED's are optimum for growing chaeto. (Note: In my research sometimes I had to visit interesting sites and forums. Thanks to the folks that grow cannabis. It appears that they put a lot of work into light optimization).

In my short note I will try to comment only about the chaeto and cyanobacteria.

Chlorophyll is a green pigment found both in algae and cyanobacteria. The chlorophyll has various states (pigments): Chlorophyll a, Chlorophyll b, Phycoerythrin, Phycocyanin, and few more others.

Chaeto has mainly Chlorophyll a and b. I think there are two more other components (c1 and c2), but it looks that they are similar to Chlorophyll a in terms of light absorption.
The absorption spectrum for Chlorophyll a has two peaks at 430 nm (violet-blue) and 662 nm (deep red).
The absorption spectrum for Chlorophyll b has two peaks at 453 nm (blue) and 642 nm (red).

Cyanobacteria has the other two pigments listed above (Phycoerythrin and Phycocyanin).
The absorption spectrum for Phycoerythrin has a maximum at 550nm (green).
The absorption spectrum for Phycocyanin has a maximum at 620 nm (orange).

The Violet UV LED's have a spectrum range from 410 to 420 nm.
The Royal Blue LED's have the spectrum distributed with a maximum at ~455 nm.
The Philips Deep Red LED's have the maximum output at 660 nm.
White LED's would have one peak at ~450 nm and the other one between 550 and 600 nm.

Combining all of the above, I think that for growing chaeto, the best is to have a combination of Royal Blue, Deep Red and some Violet UV LED's. I attached a picture for clarification.

White LED's, fluorescent lamps and incandescent lights will grow chaeto (no doubt), but a lot of energy will be wasted, consumed in a zone where chaeto does not absorb. Instead, cyanobacteria will use this portion of the light.