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Old 06-17-2005, 07:08 PM   #1
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50/50 bulb Question

Can someone explain why the actenic (sp) part of a 50/50 bulb does not count towards your wpg? It is in the visable light spectrum, and blue and green are actually two colors plants photosynthesize best. It grows algae, right? I'm not looking to argue, I am just curious why.

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Old 06-17-2005, 07:31 PM   #2
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The blue light does do little to help plants but very little, the same case with algae it helps very little.. It just isnt the correct spectrum of light for photosynthesis.. the cells in FW plants are different then the cells in the SW organisms the light is designed for..
I realize that this is a very simple explanation but I suspect that Travis will have more detailed information to post..

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Old 06-17-2005, 10:26 PM   #3
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greenmagi covered it pretty well. If you look at a color spectrum chart of actinic lighting you will notice it only spikes in the blue spectrum. Most FW plant bulbs have spikes in all three (red, green, and blue) spectrums. FW plants (and FW algae) utilize red and green spectrum light to a greater extent than they do blue light, but, as greenmagi said, they do also use some blue spectrum light. Actinic lighting does not select for algae as common wisdom claims it does. I use some actinic lighting in my tank because I like the way they make my Africans glow, but it does little to help my plants and does not grow algae
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Old 06-17-2005, 10:37 PM   #4
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Basically is boils down to this...plants can use red light most efficiently and blue light triggers the plant to take in more CO2. Any lamp that fails to provide light that covers both red and blue wavelengths will not grow plants as efficiently or produce the best colors or growth patterns. Many plants show different leaf sizes when grown under lamps that have a higher amount of a red or blue wavelengths. That being said, actinic do grow plants if they are combined with other full spectrum lamps. Personally I prefer adding an actinic lamp for the color rendering bonus it gives...but this is only advantageous if their are three or more lamps in your fixture. The 50/50 lamps are fine to use, they do not cause algae, but they don't supply the same intensity across all wavelengths that benefit plants the most.

Where the real problem occurs is when folks believe the stuff written online about how actinic lamps are useless and try to run these 50/50 lamps as low light tanks without CO2...in most situation the 50/50 lamps provide too much intensity to run a tank without CO2 injection.

Actinic usually feature a single strong but often broad peak in their spectra at about 420nm, which nicely corresponds with the absorption spectrum of chlorophyll (a and b)

Here's a brief quote from Dr. Timothy A. Hovanec of Marineland:

Plant tanks require the correct lighting to be successful. The number one reason for lack of success in growing plants in an aquarium has to be the use of the wrong lamp. Plants have two types of chlorophyll, a and b. Chlorophyll a absorbs light at 405 and 640 nm. Chlorophyll b has a peak absorption at 440 and 620 nm. Plant lamps are designed to emit light at the red wavelengths to duplicate the job of the sun. But too much red color can cause aquatic plants to grow tall and thin. For best results, use a daylight (5,000 ¡K) lamp such as an Aquasun, Ultralume 50 or Chroma 50 in combination with an actinic white or actinic day lamp. The actinic day or white lamp is a mixture of 50% actinic (blue light) and 50% daylight.
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Old 06-18-2005, 12:13 AM   #5
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I was going to be using a "daylight lamp" or 6500K.. I can tell it has the blue in it from the color it is when lit.. this sounds like I might need something else as well..
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Old 06-19-2005, 01:19 PM   #6
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the color we see with the naked eye is not indicative of true color spectrum output. 6500k should be fine.
In fact, I've tried everything from 3,000K to 10,000K and they all grow plants well, its just a matter of the color of the visible light and how aesthetically pleasing it is. 3,000K is very yellow and doesn't look that great on plants, but it makes neon tetra's colors POP right out.
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Old 06-19-2005, 04:37 PM   #7
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Ive also looked at color spectrum charts that might be making my naked eye slanted...LOL. Thanks for the reassurance there malkore!

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