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post #4 of (permalink) Old 10-07-2012, 01:29 AM
Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Posts: 11,721
Chlorophyll A utilizes a pretty good peak at 430nm and a slightly smaller peak at 662nm.

Chlorophyll B utilizes a couple of peaks, 453nm and 642 nm.

There are many other pigments in plants, and some of these are also photosynthetically active, and can utilize the light that Chlorophyll A or B do not.

The peaks in the blue area are fairly sharp. The peaks in the reds are more of a mound, the plants can utilize wavelengths on both sides of the red peak pretty well, but not so wide a range in the blue.

Chlorophyll A and B are most common in plants. There are other chlorophylls that are more common in various algae and cyanobacteria. But all the peaks and ranges are similar enough that you cannot grow plants and kill algae by manipulating the light. There is a lot of overlap in the light used by the different kinds of plant pigments.

The best way so far to see what is the optimum bulb for plants is to try to find out the PAR value for that bulb. Choose one that has a really good red and blue spectrum, often these are special plant bulbs, and then choose a bulb that fills out the spectrum and will help you to see the aquarium properly.
Plant bulbs tend to make orange fish look really weird. I find that a 'plant' bulb plus a 'cool white' or 'daylight' bulb make the tank look pretty good, and grow plants well.
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