When I was setting up the lighting on my 35gallon hex, which has a small footprint I found a powerful CFL lamp at Home Depot made by Lights of America which will fit in a very small space. The bulbs are still available at the Home Depot near my house and come stock in 6500K. The lamp I bought is rated 65 watts, and I believe they also make 85W and 100W varieties. These lamps are great for DIY setups where you are trying to maximize light in a small space without resorting to expensive metal halides.
From a quick internet search, this is what I got:
65 W 6500K CFL lamp and bulb (12.5" x 7.5" x 4") - $29.99
100W 6500K CFL Lamp and bulb (17" x 14" x 10") - $46.66
Here's mine in a custom enclusure:
From a quick internet search, this is what I got:
65 W 6500K CFL lamp and bulb (12.5" x 7.5" x 4") - $29.99
100W 6500K CFL Lamp and bulb (17" x 14" x 10") - $46.66
Here's mine in a custom enclusure: