The fixture holds 14 39w T5 bulbs.As far as what bulbs to choose,that all depends on what look you are looking for.Do you want a blue-ish,purple-ish color or a more balance daylight/actinic look?I'd prolly get the Aquactinic Constellation from Aquarium Specialty or Saltycritter.com but I going to get the bulbs from reefgeek.com. because they understand more about the color I'm looking for.At 20 dollars a pop for bulbs,I want to be sure I get the right combinations of bulbs for a bluish,purplish color yet still have the right spectrum for the corals.(mainly SPS)
I was only giving you one option...check whats in your price range,what corals you are planning on and go from there.Those websites I mentioned earlier are good place to start...try Premium Aquatics also.