The watts/gal is for fluorescent lights. Can you look into screw in spiral fluorescents, I'm not sure if they'd fit your hood. I use them on a 10g.
I can't switch the filter. It is one of those all in one hex tanks where the filter is built in to the back half of the hood and the light is built into the other half of the hood. Plus anything stronger and I think my betta won't like it much. I am not sure it isn't enough current though as the output will let my ramshorns (3/8") go zooming around in the water if they get in front of it.