What kind of light is best? - The Planted Tank Forum

 
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post #1 of 4 (permalink) Old 10-06-2012, 03:57 PM Thread Starter
Algae Grower
 
Join Date: Nov 2009
Location: Holland, MI
Posts: 137
What kind of light is best?

I have a 48" Power Compact light that takes two 96w 34" bulbs. It will be going of a 55g tank (48"x21"x12") that is low tech I am trying to figure out what lights I should get for it. What is best?

-420nm/10,000k (2 50/50 bulbs)
-only 420nm
-only 460nm
-only 10,000k
-or one of each of the above in any combination?

Would love to hear what you think, Thank you all so much in advance!
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post #2 of 4 (permalink) Old 10-06-2012, 05:04 PM
Wannabe Guru
 
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Location: Baltimore Maryland
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There's plenty of info on photosynthetically active radiation, abbreviated PAR within this forum and across the web. Please take the time to look things up.

None of the wavelengths or K value listed alone is suitable.
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post #3 of 4 (permalink) Old 10-06-2012, 05:10 PM Thread Starter
Algae Grower
 
Join Date: Nov 2009
Location: Holland, MI
Posts: 137
Quote:
Originally Posted by Steve001 View Post
There's plenty of info on photosynthetically active radiation, abbreviated PAR within this forum and across the web. Please take the time to look things up.

None of the wavelengths or K value listed alone is suitable.
I did read all the information hoppy put up about PAR and measuring it... just didn't see anything on wavelength, I was just looking for a little bit of help with that part of it.....
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post #4 of 4 (permalink) Old 10-07-2012, 01:29 AM
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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.

http://en.wikipedia.org/wiki/File:Chlorofilab.png

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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