Stay cheap. Forget injected CO2 and intense lights. In my limited
experience, Java Fern, Ambulia and Amazon Swords will grow slow but
steady in a low light tank. I can't imagine plants doing anything but
benefit your tank. They improve water quality by absorbing fish waste,
ect. Expect to dose some kind of fertilizer at you water changes
though. Generally, a tank left alone does not provide sufficient
nutrient levels for plant growth. The Ambulia grows quite rapidly in a
10gallon tank with 15W of light as long as nutrients are present. They
stay dormant if not and I've never killed one.

http://www.geocities.com/spiral_72/Spirals_page.html