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Thread: Screen lighting

  1. #11

    Re: Screen lighting

    My first post here so, hi everyone.

    Actually all algae and plants use primarily red and blue only, since that's what chlorophyll A and chlorophyll B use. They don't use green ...
    - that's correct (except for the green bit, and my apologies in advance for being picky ops: ) Chlorophyll A and B both have peaks in the photosynthetic response curve in the red and blue area of the spectrum. However, there is also a measurable (albeit, smaller) response in the green area of the spectrum. In rain forests much of the light filtering down from the canopy is green and the forest floor plants (and algae) still manage to grow. Having said that, I am not sure we should view marine algae in quite the same light as plants.

    light does not penetrate well in seawater. Red light penetrates very poorly, green light does a little better and blue light is better still. Naturally the algae have adapted to what light is available to them at the depths that they grow. So, you will find algae that grow well for any colour of light - wherever there is a niche there is an algae to take advantage of it. I believe, some algae utilise Chlorophyll C which has a peak spectral response to green light :idea: this is why I was being picky about the green :idea: So, it could be that green light is actually useful for growing algae.

    I am by no means an expert in this field and am happy to be corrected. I am just curious to what type of lighting is best, and most efficient, for a scrubber. I am presently using CFL's with 6500k(cool white) on one side and 2700k (warm white) on the other. After about 3 weeks of running my scrubber the warm white currently has better growth on it. The question is though, is it the right sort of algae? - time will tell.

  2. #12
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    Re: Screen lighting

    All algae is the right algae, when it comes to removing N and P. Red/brown turf is nice because it's so compact, but all algae do the job. After several months of testing 3000K on one side of my screen, and 6500K on the other, I'm now convinced that 3000K is better and I just ordered all 3000K replacement bulbs.

    And after several test of 14K halides, I'm convinced they are not nearly as effective at growing algae, regardless of their power.

  3. #13

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    Re: Screen lighting

    That's really interesting, I seemed to remember you having higher growth initially on the 6500k side from your photos, has it changed now?
    I can say that the 6500k bulbs I have are producing considerably better growth than the 3000k ones I had before, however they are different brands and different styles but similar power. I think it's probably just that my 6500k bulbs appear much brighter visually than the 3000k bulbs, and aren't hampered by diffusers.
    I may replace one side of mine with 3000k PL-L bulbs and see if it makes any difference too.

  4. #14
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    Re: Screen lighting

    Was not a big difference, but after turning the screen around several times, the 3000 side always had bigger lumps at the end of the week.

  5. #15

    Re: Screen lighting

    I think different lighting will favour different types of algae - it depends on what types of algae you have whether a particular light works well with them.
    Many algae do not contain chlorophyll B which would mean that much of the light between [color=#FF0000]2500K[/color] and [color=#0000FF]6000k[/color] ([color=#FF0000]650nm[/color] - [color=#0000FF]450nm[/color]) would be wasted on them. The phosphors used on CFL's only produce peaks at particular wavelengths (despite their claims!) those peaks may miss completely the wavelength required by the particular chlorophyll. Many plant grow lights (and LED grow lights) put out light at about 460nm this is great for plants with chlorophyll B but will have no effect on chlorophyll a. I am sure you can grow algae with any type of light. However, if you want to favour a particular type e.g., red turf (macro algae) then only providing the specific wavelengths required by that type should cut down on the slime, diatoms, undesirable algae etc.

    I think that the most efficient way of of lighting an ATS may be with LEDs. LEDs are virtually monochromatic so you can target the peak wavelengths of the chlorophyll* (for chlorophyll A that would be blues at ~430nm and reds at ~680nm). There are several advantages to using LEDs in this application:[list]

    low voltage (safety!)
    even light distrubution over whole of screen
    high lumen/Watt efficiency
    low heat output
    long life (10 years)
    compact
    ~monochromatic (no wasted wavelengths produced)[/list]
    Providing you make the LED panel waterproof then you could place it very close to the turf so you might get away with relatively low power LEDs.

    * other photosynthetic mechanism are used in addition to chlorophyll

    Cheers,

    Pat. Pending

  6. #16
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    Re: Screen lighting

    Where might be a good place to find what wavelength corresponds to which algae?

    As for the proximity of LEDs to the algae, did you see this?...

    viewtopic.php?f=3&t=34

  7. #17

    Re: Screen lighting

    Where might be a good place to find what wavelength corresponds to which algae?
    I gleaned all my new found knowledge about algae on the Web. The trouble is it is just snippets within biological papers and unfortunately, the vast majority of the information has no relevance to our particular application. It does take a lot of wading through to get anything useful. I think I have learned enough to pull together a summary of the different algae types and their required wavelengths. I will have a bash at it tomorrow and post it here.

    As for the proximity of LEDs to the algae, did you see this?...
    No, I hadn't, Interesting though. Clearly, to take advantage of the inverse-square law (WRT light intensity) you need a high concentration of LEDs. LEDs have a relatively narrow cone of illumination. So, if you want to move the panel close to the algae whilst avoiding dead spots you need to have them close enough together.

    Cheers,

    Pat. Pending

  8. #18
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    Re: Screen lighting

    Yes I'm thinking of .5" separation, with a prismed flat-sheet for diffusion. An advantage of closer placement (and more LEDs) is each one is lower power (and cheaper), but more soldering.

  9. #19

    Re: Screen lighting

    My original thoughts were, a thin sheet of acrylic drilled (pegboard style) for the leds to stick through. Nothing in front of the LED lens as this would reduce the main light output. Once the LEDs are inserted into the acrylic the back of the acylic panel, along with the back of the LEDs, gets painted white to reflect any stray light forward.

    When I can get round to it (also when I can remember how to use steradians) :roll: I will do the math and work out the numbers of LEDs required and their specification.

    Cheers,

    Pat. Pending

  10. #20
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    Re: Screen lighting

    So you are saying that the LEDs would not go through the acrylic, but would just be inserted into it? That might be easier than pouring liquid resin over a PCB, but would not be as thin (for two-sided.) I still think you'd need a prism diffusion sheet, unless each LED had a very wide luminence angle. The only LED testing we have so far is Snail's, who only had growth where the red and blue LED's overlapped.

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