Coralife makes a great light for just such a tank, its a 2x9w 7500k. Pretty compact, the one I have is about 9"x4"x1.5", maybe $25 if you search enough online. I have it over a much larger fuge and my chaeto has become somewhat of a algae monster, I started with a little clump about 4months ago that was the size of a baseball, now its a very dense matt thats about 20"L x 12"W x 8" thick and it's overflowing with pods, snails, even a HUGE teddybear crab calls this clump of chaeto home. My fuge is barebottom, or rather has a thin layer of LR rubble. I like things simple and my fuge is made out of a 45g tank, inside of this tank I placed a 5g smaller tank that both of my overflows drain into, also inside of this 5g tank sits my Needlewheel skimmer, I used this design because no matter what, the level of the 5g tank never changes, no matter how much evaporation there is, so I never have to adjust my skimmer. There are return pumps at each end of the fuge, no micro bubbles, took 5 minutes to make, cost $45 and I have tons of micro life and no micro bubbles..
