Get a Fluorex lamp. I special order them through my local TrueValue branch for about $30 a pop. They're about 7"x10" and one could easily light your tank - they burn 65W and are roughly equivalent to a very-high-output (VHO) lamp like a 500W metal halide. They're based on high output/power compact fluorescent lamps, like Clint is talking about. I use two with my highland Neps and I'm getting reds and purples out of plants that aren't even supposed to develop leaf pigment.