You asked your fert questions elsewhere, but for the purposes of this thread, I just remembered this tank, which my mind blocked out of memory but ran for around 6 months with super high CO2 and my at the time inquisitive nature of dosing and goofy ideas (this was a great learning tank). More importantly, it used a 40W CF (Current? Coralife? Its around here somewhere...) and amongst those plants you'll see Rotala mini type 1, Rotala "Goias", Eriocaulon "Guang Zhou", Rotala rotundifolia "colorata", legit Rotala indica (back then it was Ammania sp. "Bonsai"), Rotala pusilla, Tonina fluviatilis, L. "Cuba", Rotala macrandra (both regular and narrow), "Purple Bamboo", HC, and other stuff Plantbrain called weeds. Seriously: could grow whatever I wanted. This was also the tank that got me over light. And the tank whose greenwater defeated me and made me cry like a little boy. There were better pics somewhere but that site disappeared -- these pics are a couple years old. Anyway, seriously, read up before running that much light and jsoong's suggestion will let you have whatever garden you want.
Incidentally, the annoying part about springing for a nice 20" fixture is you'll never be able to upgrade size without looking ghetto. If you can invest the time and money on a nice DIY fixture, consider something like 30" for 20 gallon long (which is a great size) so you have the option of, say, a 29 gallon later (never had one but sure is a nice shape). Then you'll need to reconsider lighting options and stuff but AH Supply's options are definitely nice and have a long track record of happy customers.
