A fluorescent strip light on a standard 5-gallon is probably 14 watts. Despite being virtually 3 watts per gallon, I would treat that as a low-light tank. There is only so much you can grow under a 14-watt fluorescent bulb, no matter how small the tank. (This is why the WPG rule doesn't work as well in small tanks, as Leopardess mentioned.)
However, the good news is there are still a number of good-looking plants that you can grow with your setup.
Marsilea quadrifolia is often recommended as a "poor man's glosso" because it looks like a scruffier version of that popular carpet plant, but does not require high light or CO2 injection. It is actually a fern, but looks like a water clover.
Dwarf sag could work too, like Leopardess said.
These are both slow growers, so definitely take the skipper's advice and incorporate some fast-growing plants. I'd add
Rotala rotundifolia (AKA
Rotala indica), to Leopardess' list. I've gotten to grow nicely under 15 watts in a 10-gallon (in standard gravel), so I imagine it would work in your setup.
Hornwort is a mixed blessing because it supposedly releases an algae toxin, but if it doesn't like your tank, all those needle leaves make a mess -- like a "Christmas-tree-in-February"-type mess.
Another fast grower is pennywort (
Hydrocotyle leucocephala), which I have growing nicely in a 5G/14W betta tank right now.
Leopardess gave you some good info for constructing a high-tech tank, but if you're just starting out with planted tanks, I'd recommend you try it out with your current setup first (though it'll be helpful to change the substrate to something more plant-friendly -- I like CaribSea's Eco-Complete).
A high-light, CO2-enriched, fertilized 5-gallon tank would be very challenging for a beginner IMO. The small tank is difficult with plants for the same reason that it can be tough for fish -- it is easy to throw the water chemistry out of whack.
With a high-tech 5-gallon tank, you would not have much room for error on ferts or CO2 before you were looking at an ugly algae outbreak.
On the other hand, using your current low-tech setup, you would be able to take things more slowly and let the fish waste do much of the work, fertilizing only if you noticed a glaring nutrient deficiency. You would have more time to observe growth, notice problems, and make adjustments.
Since you are looking for low maintenance, it is probably best to keep things simple for now -- especially since you've already purchased some equipment that is perfectly adequate for a low-stress planted tank.
Hope that helps.
-John
Edit: Fixed link
