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K rating on bulbs and Plants.

Discussion in 'Lighting' started by PlantedFishGeek, Sep 23, 2008.

  1. PlantedFishGeek

    PlantedFishGeek Junior Poster

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    Ok i hope gets me a solid answer without sparking a massive debate. What Kelvin rating on the bulbs should i be running, i have looked at bulbs on a number of sites and they have 3000k,4000k,4100k,5000k,5500k,6000k,6500k, 6700k,8700k,9000k, 10,000k, 12,000k,14,000 I have even seen 20,000k bulbs but those were MH. There are also 50/50 bulbs,Actinic, Fiji Purple bulbs, and the Weird pink "Plant Grow Bulbs" All this is a bit much for the Average Joe to sort through and figure out.

    Here is some info the "website" lists not sure on accuracy,6500K for rooting and vegetative growth stages.3000K for flowering and fruiting growth stages.4100K spectrum for rooting and vegetative growth stages.5000K for rooting and vegetative growth stages. It is just confusing, does this mean i need one of each of these bulbs?? Or will a 6500k bulb do everything that a 3000k,4100k,and 5000k bulb will do?

    I have a 10,000k bulb right now.

    Is there an "Ideal" K rating for a planted tank,if so what is it?

    Are 10,000k bulbs good for planted tanks?

    So What K rating is best Avoided in a planted tank?

    If it should be a mixture What K ratings are Best?

    Please Answer the above assumeing CO2,Ferts, Etc AND for a low tech no Co2,no fert tank.

    Thanks in advance!
     
  2. Carissa

    Carissa Guru Class Expert

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    Anything from 4000K - 10000K is fine. Pick what you like the looks of.
     
  3. PlantedFishGeek

    PlantedFishGeek Junior Poster

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    None are more effective than others? A balance isnt needed? I have often wondered if maybe my 10,000 wasnt part of why i have problems with plants, because the mosses i have in my smaller tanks under a 6500k bulb look far better!
     
  4. VaughnH

    VaughnH Lifetime Charter Member
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    I would say between 5-10.000K is a good rule of thumb. That number is not a real color temperature anyway. Fluorescent bulbs emit light depending on what phosphers are coated on the inside of the bulb, with each one contributing one spectrum line. The "best" bulbs have 3 phosphors, so they have a more even spectrum than those having 2 phosphors. If you have plants and or fish that have red, and you want to see the red, you need a bulb with some red in the spectrum. The highest numbers usually are the bluest white light, sometimes lacking in red color, but not always. The GE 9325K bulb isn't blue white at all - it is a red violet color, which is jolting the first time you see it, but then your eyes adjust and you notice how beautiful the reds in the plants and fish look. I have read that the 8800K bulbs do a similar thing.

    So, it comes down to what looks best to you. Actinic is generally beleived to produce light too far out of the spectrum of light that plants need, so they are useless for a planted tank. And, they have a single phosphor, as I understand it.
     
  5. ceg4048

    ceg4048 Lifetime Charter Member
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    Hi Hoppy,
    I agree with the first sentence but not the second. Plants uses any light energy in the visible spectrum. Therefore if you can see the light then plants can use it. Actinic peaks in the 420 nm range which is blue. This is at the lower region of the visible spectrum but still quite useful. If the entire tank were filled with actinic light then the plant would fabricate auxiliary pigments in order to convert this wavelength to other useful wavelengths. Having said this though a tank completely lit by actinic would look very dim to our eyes since human vision is optimized around the green wavelengths, however they can have a very nice effect when used in combination with other bulb colors - with no disadvantage whatsoever. In fact, blue is the highest energy visible light since it has a shorter wavelength and higher frequency. I don't have a PAR meter to confirm but it wouldn't surprise me at all if an actinic bulb delivers a higher photon flux compared to a red bulb of equivalent power rating.

    Get any bulb that looks nice, without regard to K values and your plant will use it. In any case, as hoppy points out, the K ratings of bulbs are almost strictly propaganda as they seldom adhere to the black body radiation Kelvin scale.

    Cheers,
     
  6. Carissa

    Carissa Guru Class Expert

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    This is interesting to me. I've wondered if it really makes a difference if you have a wider spectrum of light or not. Actinic bulbs are very narrow in spectrum, which is the only reason I can see that it wouldn't be useful light. I've read that blue light actually has the most penetrative power in water (as evidenced by the fact that in very deep water, everything looks blue), also I thought that actinic bulbs were created to simulate the spectrum you will get in deep water. But in our relatively shallow tanks, I'm not sure if having extra blue light would really matter much as far as having extra penetration power. Also, you can buy "full spectrum" plant bulbs. Are these just a hoax more or less?
     
  7. beastboi

    beastboi Junior Poster

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    From my understand 6500k is the best for plants, 10,000k does nothing for the plants at all.
     
  8. Carissa

    Carissa Guru Class Expert

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    This can't be true....I have 10000K bulbs on my tank and my plants grow just fine.
     
  9. aaronnorth

    aaronnorth Prolific Poster

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    the reason most people reccomend 6500k is because it isnt too blue or red, it shows off the green colours of plants and it is 'supposed' to be similar to the suns colours which in turn is 'supposed' to make the plants grow better

    But it doesnt!

    If you go with 2 tubes, i would go with a 6500k & a 4000k, this way it will show off the all natural colours of plants, a great combo IMO.
     
  10. Gilles

    Gilles Lifetime Members
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    Well you are all wrong, in a way. Not that i am the expert but it all comes down not to what colour temperature the light is (e.g. that is only for us to see) but what spectrum the bulb emits. There are those who emit more red, those who emit more blue, just like ceg4048 is telling.

    On my tank, i have Philips TLD T5 HO 830, 840 and 865. Which means; 3000K, 4000K and 6500K (e.g. natural sunlight).

    Other than that, there is the lumen question. How many Lumen does a specific bulb emit (lumen versus Watts). There is a dutch article ( Licht in het aquarium ) which explains it all very detailed and also mentions the lux that certain plants require to grow optimal. I have no enligsh translation but maybe there is a dutch to english translator?
     
  11. ceg4048

    ceg4048 Lifetime Charter Member
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    Full spectrum is irrelevant and is not even true. No bulb is full spectrum because no bulb can approximate the spectral curve of the sun.At best a so-called full spectrum bulb has energy peaks in more than one frequency and that's it. Even if it were possible to simulate the solar spectrum it wouldn't matter because very few plants in tropical rain forests have access to full spectrum lighting, especially if they are in water which attenuates many wavelengths. Possibly, open grasslands or the very top leaves in the canopy trees of the rain forest have access to full spectrum lighting. 300 feet below the canopy in a stream stained with tannic runoff aquatic plants grow fine without ever seeing full spectrum or 6500K light bulbs their entire lives. As a result plants have developed the ability to utilize whatever visible light is available in the environment.

    Freshwater does not attenuate the red, green and yellow wavelengths as strongly as salt water. As a result, freshwater appears as many different colors while marine water normally appears blue or blue/green. Blue light is a higher energy radiation and so is not affected as easily by the water. This is why it penetrates. Red light is the lowest energy visible radiation so it is the first victim upon entering seawater. The zooplankton, corals and other species living at certain depths have had to adjust to the spectral quality reaching them at that depth.

    Photosynthesis requires photons within the visible spectrum. Lumens are not relevant because it's a measure of how humans perceive the brightness of light. Chlorophyll and auxiliary pigments such as carotene molecules are sensitive to and eject electrons when struck by photons in the visible spectrum. Each chlorophyll type is optimized around a certain spectral band, however there are enough different pigment types to cover the entire spectrum. The plant assesses what wavelengths are available in the environment via photoreceptors and manufactures pigments to match what is available. The photon energy is then converted and passed on to the chlorophyll for electron conversion. If the spectral quality of the light changes the plant adapts and manufactures a different pigment type to match the new ambient conditions. Although Chlorophyll a and b are the dominant pigment types other pigment are always present. You can see these pigments inherent in the leaves during the Autumn when the green chlorophyll is withdrawn leaving the other pigment types behind. These pigment are responsible for the fall colors but they are not just there for our viewing pleasure. They are there to take advantage of whatever wavelength light is available during the growing period.

    Therefore it does not matter what color light is used, the plants will adapt to match.

    Cheers,
     
  12. Carissa

    Carissa Guru Class Expert

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    So how does it work - do plants adapt their color to match the spectrum, or to not match? Because if a plant looks green, it must be reflecting only green light, doesn't that mean that all other wavelengths are being absorbed and used except green? Or is it only using green?
     
  13. aaronnorth

    aaronnorth Prolific Poster

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    They dont change their colour in any way, if we put a blue light their pigments woudnt change blue resulting in the plant turning blue!

    They adapt to the wavelength (nm)
     
  14. Carissa

    Carissa Guru Class Expert

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    Ok, so basically the chlorophyll dominates what we see, but there are other invisible (to us) pigments that are utilizing light too? My question is, basically, in what way do they adapt?
     
  15. aaronnorth

    aaronnorth Prolific Poster

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    yes, chloroplasts contain chlorophyll pigments which basically contol the colour of the plant, this is why red plants are more demanding to light because they have less chlorophyll pigments.

    quote from Clive in earlei post
     
  16. VaughnH

    VaughnH Lifetime Charter Member
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    When you see something green, it isn't reflecting just the green part of the spectrum and adsorbing the rest. It is just reflecting more green or a mix of other colors that look green, than it is the remaining colors. A green plant is reflecting more green than other colors, so it looks green. Look at it with a non-green light and it doesn't look black, it just looks a lot darker. Like almost everything in the natural world nothing is as simple as it looks.
     
  17. PlantedFishGeek

    PlantedFishGeek Junior Poster

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    Ok so basically what you guys and gals are saying is that i can go to walmart, Buy what ever Light bulb is cheapest and as long as i have enough WPG getting to the plants they will grow?
     
  18. aaronnorth

    aaronnorth Prolific Poster

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    yep! :)

    Thanks, aaron
     
  19. PlantedFishGeek

    PlantedFishGeek Junior Poster

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    After reading the following again it kinda sounded confrontational that is not my intent i really am confused buy this.

    Ok then explain something to me cause now i am really really confused.


    Why is it that when i was running 2x 10,000k over my 55g tank at 1.96 WPG, my moss looked Brown and was Dieing off, BUT a section of the moss from that tank has Turned completely around and is a nice green in my 10g shrimp tank under 1 20watt 6500k "twisty" bulb? The 55g has a much higher bio load therefor much more food available to the moss. Neither tank has CO2, and Neither tank gets fert dosing. Now if what your saying is true, then the moss should have been just as green and healthy in my 55g If not more so because there is more nutrients available due to more fish poo.
    Explain this please?
     
  20. phanmc

    phanmc Lifetime Charter Member
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    Higher light (wattage) drives growth as well as CO2 and nutrient demands. Since you are not adding any nutrients and are relying solely on fish waste for nutrients, you are likely deficient in some nutrient that are not present in fish waste, like K or micro nutrients.

    I know I am able to grow moss in pretty much any K rating, from 3,000k-18,000k.
     
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