I have a 10 gallon tank that has the standard hood with 2 screw in sockets positioned horizontally. I use the spiral cfl bulbs, 18watt with 6500k rating. The k rating is important to be around 6500 for plant growth. I only use 1 of these bulbs in my 10gal as 2 was way overkill. I have a little algae growth as is, but I don't mind some as it's a shrimp tank, so they have some permanent food source. Most home improvement stores will sell a similar bulb your friend could use. I'm not sure about par etc, as most of the par figures are done for the larger T8 bulb setups. But if he's going low-tech, a 13-18watt bulb should be fine, and he would only need 1.