[Raymond S.]

It will brobably work but I'd change it to a GE "Daylight" bulb from Loew's which
says 6500K on the package. That's if you don't want an "aquarium bulb" type.
Doctors Foster & Smith on-line has good prices on those.
Zoo Med has two bulbs good for plants(actually more but for the 20H tank) that
only cost $10 at that Doc F&S place. The Ultra sun for brightness is good for plants
as it's 6500K and the Flora sun is great for plants but doesn't have near as much
brightness as the Ultra sun.
If your tank is doing good and the plants are growing(both of those grow slwly anyway) then I might not change it at all. Those 6500K bulbs may cause algae
in that tank and you would then need to lower the amount of hrs they are on.

 

[lauraleellbp]

Your GE bulb should work just fine. It has some good spectrum peaks in the right area to support plant growth (click on the "plant and aquarium" option in the table at the bottom of the page):

http://www.gelighting.com/na/business_lighting/spectral_power_distribution_curves/

15 watts from a T8 light fixture over a 20gal is very low light, but should be sufficient for the plants you're currrently keeping.