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Thread: Violet edge of spectrum and algae

  1. #11
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    I'll chime in here with something. All of the LED grow light fixtures that you see on the market are almost exclusively 660nm red and 455nm blue. This is the red that corresponds to the Chlor. A peak and the blue that corresponds to the Chlor. B peak. So why mix them? If one were trying to hit both peaks, why wouldn't you throw in 630s and 430s as well? Simple. Money. Violet 420-430 LEDs have not been readily available at a good price point. RBs are a dime a dozen comparably.

    However, as it is becoming apparent that the spectrum coming off T5HO/VHO actinic and MHs is excluded in most LED build (stock or DIY), people are noticing things that don't work the same. Hence the demand for Violet is rising and price is dropping as supply ramps up.

    I for one will be re-visiting my "light experiment" and putting together some test scrubbers. In reality, the 660nm Red should be paired with 420-430nm Violet for hitting all of Chl A. BTW the Clh A is the primary wavelength put out by the sun, and the "B" bands (455 and 630) are used during sunrise and sunset. At least that's how I understand it.

  2. #12
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    Quote Originally Posted by Ace25 View Post
    ..., bought a $60 "bucket" of it, and between my 2 tanks and having to replace it every 3-4 days it only lasted me 1 month....
    I did not even know that rising P is such a big problem. I have teaspoon of GFO on my tank and exchange it every 4-5 month. My thinking was that if it be primary phosphates reducing medium, then let it be expensive and time consuming. But it is only to help and stabilize what ATS is doing... Now I see how bad this is.

  3. #13
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    FLoyd , I have bought few 420s. Will put them on tank immediately after receiving and report results. What proportion would you recomend 660+420 ? 5+1 or 4+2 on 15sq in.

  4. #14
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    ideally the ratio is 6.5:1 red:blue but I'm not sure if that is a ratio of intensity, LEDs, radiometric flux, etc. If I had to take an educated guess, I would say the last one. 455s are more intense than 660s, but the 420-430s are of a lower (visible) intensity and RF might be lower as well. So for your screen go as high of a ratio as you can, 5:1 is good.

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  6. #16
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    " Two peaks of effectiveness were found, one near 450 mmu, and another, as yet ill defined, in the near UV. "
    So one of them we already use. I have found leds for seccond possible peak in two wavelengths 420-430 or 390-405. Would be nice to know witch one suits better.

  7. #17
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    What do you make of this then;

    http://www.controlledenvironments.or...enger text.htm

    Quote from which;

    "CONCLUSIONS


    As for higher plants, growth and development of algae depend on light. Besides the light necessary to facilitate photosynthesis, UV-A/BL is of specific necessity for the normal development of algae. Spectral output of artificial light sources should match as close as possible the absorption cross section of the pigments responsible for photosynthesis and morphogenesis. The irradiances of the incident light should not exceed saturating values for photosynthesis to avoid photooxidation. By choosing the appropriate light source one or the other taxonomic group can be enhanced or suppressed in growth and development in comparison to others."

    This may have implications that are far ranging. Comments welcome. May be of especial interest to
    Floyd.

    Gonna rig my uv tube up to trial this I think. Seems cfl's already emit a low level of UV, but nowhere near natural light.

    http://oee.nrcan.gc.ca/residential/personal/2713

  8. #18
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    Interesting. Could throw in a UV LED into the mix. The problem becomes that UV is dangerous in that you can't see that the emitter is working and you can do damage to your self if you're not careful. Plus they're expensive.

  9. #19
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    Wonder if an actinic tube will suffice for my test. It should certainly penetrate the screen at least, and probably reduce the risk of frying the algae.


  10. #20
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    Regarding LED's , what spectrum should we target on ?

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