Re: Aquatic Plants Digest V1 #385

Greg Tong, <gtong at sirius_com>  wrote, Wed. April 3:

>In an article in one of the fish magazines recently, I read a
>recommendation for adjusting the color temperature of our lights by using
>photographic gels. The gels are colored plastic sheets generally available.
>The idea is not to worry about the color temperature of the lights when we
>buy them but to adjust them to what we want by placing the gels between the
>lamps and the water in our tanks. Of course, the gels would have to rest on
>glass or some other rigid thing.
>It strikes me that this might work for adjusting color temperature but
>might also reduce the lumens that reach the water. Any
>Greg. Tong
>San Francisco, CA, USA
>gtong at sirius_com
>"Every infinity is composed of only two halves."
The only thing the gels can do is absorb a lot at certan wavelengths and
very little at others.  They can cut out parts of the spectrum, but they
can't add any light energy to any other parts.  Since plants preferentially
absorb in the red and blue regions, the gels had better not cut out any
lumens in those regions.  In fact, if they reduce the transmitted light at
any wavelengths where the plants absorb even a little of the light energy,
they are cutting down on the over all light energy that the plant would be
absorbing if the gel wasn't there.  So, the way I see it is that the gels
can hurt, but can't help.  The same argument applies to those "plant
lights" I sometimes see that are just incandescent light bulbs with
blue-tinged glass.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174

Where students and faculty are suffering from spring fever!