Wal-Mart Fluorescents

Yes, I've used them and they work. The GE Sun or Sunlight bulbs are nice too!

How many watts vs how many gallons? you want generally 2.5-3 watts of light per one gallon

ive tried these bulbs with no success, since it was only something like 18 watts and i have a 20 gallon tank

GE Sun bulbs, ive been hunting for, if theyre the right wattage, youll see some results.

Bulb types dictate the wattage more so than the manufacturer. They're not like incandescent bulbs were the wattage can be increased in the same size bulb. Using typical T-8 or T-12 bulbs the only way to increase wattage is to use more bulbs. Though certainly not cheap, compact flourescents are a reasonable route. Don't forget that all of this high wattage has only become common in the last dozen years or so. Many FW fish prefer the tank much darker and there are low light plants. My tanks are packed with Java fern and floating water sprite using a single T-8 lamp. Here at 1 watt per gallon I still trim and discard handfulls of plants every three months or so. I also grow some anubias, hygrophilia, and in the past crypt's.
To realize the full effect of high wattage lighting you also need CO2 and fertilizers so the plants have the nutrients needed to grow at the rate possible by the lighting. Unless a true planted aquarium is your goal that's a lot to invest in for some plants.

ghinksmon said:

... They're not like incandescent bulbs were the wattage can be increased in the same size bulb. Using typical T-8 or T-12 bulbs the only way to increase wattage is to use more bulbs.

Click to expand...

You can overdrive normal flourescent bulbs a.k.a. ODNO (OverDriven Normal Output) but ghink is right, the size of the bulb dictates the wattage. T8s of same length as T12's are lower wattage but supposedly produce the same amount of light therefor are more efficient.

Another note on the shop lights...

These lights aren't built for the high moisture environment. Be sure you have a tight fitting lid to minimize the moisture rising up to the lights. Also the light should probably be a few inches above the tank for air circulation.

When shopping for bulbs take a look at the color temperature. Many Walmart bulbs are over 5000K, and a few are at 6500K. The daylight bulbs are the ones that typically work the best.