Re: Aquatic Plants Digest V2 #116

>From: "E. Keith Johnson" <zekj2 at Access_ETSU-Tn.Edu>
>Date: Fri, 02 Aug 1996 16:03:55 -0400
>Subject: Lumens vs. CRI?
>I'm trying to decide between two T8 fluorescent lamps for a double
>fixture over two dwarf cichlid tanks (20L) which will also contain
>dwarf species of swords...
>Initial Lumens:  1300
>Mean Lumens:  1160*
>CRI:  80
>Initial Lumens:  910
>Design Lumens:  850
>CRI:  98*
>All specifications and other factors are basically the same except
>the lumens and CRI.  I like the lumens of Lamp 1, but the CRI of Lamp
>2.   Comments?  Which would be a better choice?  I feel the light in
>either case is adequate for the tanks.  Since the fish are Rams, I
>like the higher CRI to enhance their colors.  Would it make sense to
>use one of each in the double fixture?
>E. Keith Johnson
>East Tennessee State University

Keith, Knowing lumens & cri alone is not enough information to choose
between the two bulbs, you need to know the spectrum. The plants may not
"see" the wavelengths they need.

The higher cri would be more likely to contain light os the proper wavelengths.

Mixing tube types is always a good idea. Flourescents do not put out light
of all wavelengths, but generate "spikes" of spectra. Mixing tubes
(phosphors) results in overlapping the spikes to create light closer to
continuous spectrum.

-Bill Brady