If you go to wal-mart, they have 6500k bright white Power Compact screw socket bulbs.
5 dollars a piece.
They provide the light required for plantgrowth and are perfect for salt and freshwater aquariums.
If you take a look in the DIY
section, I built a hood for my 10gal with these types of light wired it.
You'd need sockets that don't have a on/off switch on them, and the onlyhh ones I've found that don't have that are weatherproof sockets.
Weatherproof sockets are a good thing to use, anyways, since they're weather proof! :p and their going to be in a moist enviroment.