Proper wattage?

what kind of bulb??

I get mine on-line from
http://www.bigalsonline.com/

http://www.drsfostersmith.com/product/shop.cfm?c=3578

There are tons of other places to get lights from. What type of plants do you want? This will help you determine what type of lighting you need. General all purpose plants 6700k-10,000k daylight bulbs.

To answer the question as posted:
I'd go to HD/lowe's/lighting place and get a GE/philips/osram brand Daylight bulb...wide spectrum ~6500K. Reasonably priced, and works fine for low light plants such as java fern, java moss, anubias, and maybe crypts. I wouldnt bother with the expensive tubes.

I'm guessing this is a single tube T12 fixture? 24" or 30" bulb? a 24" is going to give you less light near the ends of the tank.
The wattage is going to depend on the fixture...all 24" T12 tubes will be the same wattage (~20W) +/- a bit....you can't get a 40 watt 24" tube, for example. Read up T8 vs T12...

Or...you could go buy an electronic 2-tube ballast and overdrive the single tube for a bit more light. That would take some DIY'ing

Now if the question was: "How can I light this tank well & cheap?" I'd say...get a glass top (or go open-top) and hang a 2-tube shoplight with T8 daylight tubes over it. I have that over my 20long (same footprint as a 29); it's plenty of light for low-light and some medium light plants. I have mangroves (think Florida backwaters) growing in it.

changing bulbs wont help you. you need more light.like said above you can use t-8 shop light.
i have some 29g tanks now, and my low light has a 65watt bulb on it and is on 7hours a day to keep the algae down.
grass like plants and marimo balls need medium lighting around 2.5wpg to grow.