This is the light that came with my sump. It appears to be missing one end of the fixture itself and there is no bulb in it. What kind of bulb should I purchase?
IMO I would chuck that if it's missing an end of the fixture. You can get a cheap CF bulb at walmart and just use a lamp. It's not worth a disaster to have it fall or short out. I use one of those crappy plastic hoods that comes with new tanks and just run a 50/50 bulb but that's only because I had it. Macroalgae appreciates daylight.
+1 Amba
I would personally go buy one of those Eco Friendly compact fluorescent bulbs, and just plug it into a normal lamp fixture. Less cost, less worry.