30 Watt 55 G
Hello lilj...
Believe it or not, there are a number of plants you can grow in low light and if you get a little creative and float some of the moderate light plants attached to long pieces of driftwood, getting them close to the light source, you can grow those too.
I have large, low light tanks and grow Anubias, Java fern, Cryptocoryne, Singapore moss, Pond and Peace lily, Water wisteria and Pennywort.
I also have Banana lily attached to driftwood and floated. It grows well under just a single 32 watt T8 or 40 watt T12. Water wisteria and Pennywort will also grow well floated and attached to driftwood with thin, black sewing thread.
The local hardware stores carry 48 inch, GE aquarium plant bulbs for about $10.00 each and they'll easily last a year. Keeping large, planted tanks can be pretty inexpensive if you do your homework.
B