08-29-2003, 01:30 PM
Join Date: Feb 2003
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by chinaboy1021:
im confused on which bulb i should get for my 20 gallon. ive read too many times that plants "use" 5000-6500K. but GE 9325Ks are good because its high in both the red and blue spectrum, which plants use most.
so i dont know if i should get a 5500K zoomeds, or 18000K aqua-glo.<HR></BLOCKQUOTE>
Plants do "use" 5000-6500 K, because that's the temperature of the sun, depending on your latitude. It is around 5500 K in the tropics. However, the sun is a black-body radiator, which means it has a normal distribution of radiation, with a peak at a wavelenght (yellow) of light corrsponding to a hot body radiating at 5500 K. No fluorescent tube has that characterisitic. They all radiate from phosphors, which have "line" spectrums. To get white light, a tri-phosphor bulb uses, say, red, green, and blue phosphors. The difference from one tube to the next is in the phosphorescence of those phosphors. This all make "Kelvin" ratings a lot of bupcus.
You should really pick tubes that make your aquarium look good to your eye. Get enough of them over the water to make the plants grow. Then you will be happy.