Originally Posted by Bang Guy
Originally Posted by steve-s
The higher the number the more blue/violet the light spectrum emitted.
Please compare the spectral output of the 6500K Iwasaki 250 watt Mercury Vapor bulb and the 20,000K Osram 250 watt Metal Halide Bulb. You will see that the Iwasaki bulb produces more light in the blue/violet spectrum than the Osram and yet the Kelvin color is far lower. This is because Kelvin is just the final color of all the mixed wavelengths of light.
Couldn't find a 250 comparison but I did find a <<400w spectrum plot>>
unless you'd like to hook me up. I was not trying to dispute the 6500k would not produce in the 390-490nm range. What I was suggesting from the start was that the higher kelvin rating would emit measurabley lower output in the 600nm range allowing the hobbiest to "control" if you will, the growth of different types of algae a little better. Especially in a newer nutrient rich system where all forms of micro/macro algaes will be competing for existance. The lowered amount of red spectrum would lessen the nuisance algaes giving the chosen macro's a better advantage. It has at least worked for me in the past.
Most of the lights we use produce the full spectrum of light just at different peaks depending on manufacturer and equipment used to drive them. While we are specifically speaking of fluorescent type bulbs I could not find any specific data plots on their color spectrums but I would assume they would be at least similar. Photosynthesis will occur in a wide range of spectrums but different species will utilize some spectrums better than others.
I do have to agree on the kelvin point though. While there are subtle differences, all are very similar in nature.