01-02-2013, 01:02 PM
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Originally Posted by FishyFishy89
Right, but there would be 2-3 of those bulbs. Wouldn't that make the Kelvin rating at 10k or 15k?
Jentrala is correct in responding on this. The Kelvin is the colour temperature [nothing to do with "heat" temperature] of light as we perceive it. Sunlight is around 6000K [can't remember the exact number off the top of my head] and light with a lower K number is more "warm" while light with a higher K number is more "cool" in appearance. Warm involves more red and less blue, and cool involves less red and more blue.
Scientifically controlled studies indicate that aquarium plants respond best [= faster photosynthesis, all else being equal] to light between 5000K and 7000K. The most successful tubes over planted tanks are those within the 6000K to 7000K range. The "daylight" type are around 6500K so these are right where you want things. With more than one tube over a tank, you can mix the K to suit your preference for hue; a 6500K with a 5000K will provide good light for the plants but have a "warmer" tone, whereas a 6500K plus a 10,000K will be "cooler" in its tone.