[StirCrazy]

Originally Posted by Myka

I don't know about that... red (yellow) light has more photosynthetically usable light than white light does, and blue light has even less. That's like grade 9 biology. I don't know how that applies to aquarium bulbs since there are so many variables like amount of energy put into the bulb and different brands.

there is no white light, white is an effect from combanations of other light colors. thats why there is no white strip in a rainbow.

Photosynthetically Active Radiation or PAR, is from about 380 to 720nm and all forms of light can power photosynthis, the differance is what is more available and what plants have adapted to. If I remember right from hortaculture (corect me if I am wrong) red light will produce a fast growing but spindily plant, where blue light will make a slow growing but stockey plant. we did exparaments growing the plant under blue domanate light for root development and then switched to a red domanat light to increase folage and induce flowering.

Visable light starts at 400nm with Violet, and ends at 700nm with red in between we have blue green yellow and orange

you can produce a white looking light with different combanations of reds, greens and blues (primary colors) this is why we can get different PAR levels from white lights of different brands. one brand might have very high violet/blue and a spike of red and hardly any green and look white, another might have red, green, and blue all at the same levels and it will look white also.

as far as strenght of the wave lenght go the shorter the wave lenght, the more power it has, this is why blue light is domanate in deeper water and the green and red light gets filtered out.

Steve