Lighting for planted goldfish aquarium

To revisit this, (and cross it over to rafp, which I didn't even know
existed when I started) recommendations for lighting (based on what
particular plants require in the aquarium) are generally given in "watts per
gallon" Well, I did some research on how much light is produced per watt by
different types of lighting systems as follows:

Tungsten Incandescent: 5-17.5 Lumens/Watt
Quartz Halogen: 24
T12 Fluorescent: 50
Compact Fluorescent: 45-60
White LED: 26/70 (some prototypes are running up to 150)

Metal Halide: 85-95
T5 Fluorescent: 104

So the question when trying to judge such recommendations remains "watts of
what kind of light?"

Example: Ludwigia Repens (one of the plants in my aquarium) calls for 2-4
watts per gallon. 58-116 watts in a 29 gallon tank (my tank size). The
problem 116 watts of T5 fluorescents is about six times as much light as 116
watts of Tungsten incandescents. If the recommendation referred to
incandescents, then 20 watts of T5 fluorescent would serve. (All of this, of
course, assumes lights with spectra that are reasonably useful for the
plants.)

One thing I note, the metal halide lamps, they are less efficient than the
T5's, but they do pack a lot more watts into a smaller package. Which just
goes to show that "efficiency" is not the be-all-end-all of the matter.

--
David L. Burkhead "Dum Vivimus Vivamus"
"While we live, let us live."
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