I think that I figured out a pretty good lighting solution for this setup. It is difficult to find a fixture to light up the 18" width of this tank.
This is a pair of trouble lamp reflectors that I put together with a dual-socket ceiling fixture. It attached real secure to the metal shelf bracket with the threaded knob at the top of the socket assembly.
I will install two 16w 6500K daylight CFL bulbs and this should provide a real nice light for growing these plants. I also intend to cut the hooks at the top of each reflector off because they will just catch on my shirt sleeve. I just need to go to the hardware store to get a couple more items and then I can put this together and hang it up.