i'm running Sunlight Supply TekLight T-5 "all in one" fixtures. My tank is 83" long, so I have a 4' fixture butt-jointed to 3' fixture. Turns out 4' and 3' are each a little shy of the stated footage, so they are about 82 3/4" end-to-end. Both are 6-bulb fixtures.
As far as bulbs, I'm running 2x 10000K, 2x 12000K, and 2x 20000K in each [from memory i think they are called "white," "blue+," and "actinic blue."] I intersperse them as... W, B+, AB, W, B+, AB ... in each fixture. The combination gives a pleasing overall white-ish blue color temp, with the pure actinics giving an incredible POP on all of the fluorescent pigments in the tank.
--SM--