After looking over my old pictures and checking my records I've concluded that those screw in fluorescent bulbs are utterly worthless for growing plants.

This is a picture of a tank of Cryptocoryne undulata. The tank is a 30 gallon "long" and was set up around 1996. The substrate is playbox sand. It had a single 20W fluorescent tube.

I'd switch back and forth between gro lux and a 5000 or 6500K tube every six months. Look at the density of the stems coming out of the gravel in that era:

In 2000 switched to two 24W screw in fluorescents figuring 48 watts of light HAS to be better than 20W in the T12 tube. This is how it looked in the fall of 2004 (click for larger images):

Guess I figured wrong. It never grew as well, big or fast as when I half half the watts but a more appropriatly shaped tube.