Best bulb I've found is "SYLVANIA 2-Pack 23-Watt (100W) Spiral Medium Base Daylight CFL Bulbs" at Lowes. About $10 for a two pack and they are 6500k. I use mine with a ~$10 plastic hood, gooseneck, clip on light fixture also from Lowes. The clip is plastic and very strong.
Best combo I've found and those bulbs grow Chaeto like crazy.