I'm gonna use 2, 4-ft bulbs in addition to the 2, 2ft lights that came with the tank. I'm gonna build a canopy and add the 2, 4-ft bulbs to that. I've already purchased a ballast. This will be a hap/peacock all-male tank. I'm still working towards setting it up, but I already have the tank and most of the stuff that goes in it. I think 4-ft bulbs should work okay in a 5-ft tank.