I think the 55 gallon tanks lend themselves very well to ultra-low
budget lighting. Walmart sells dual-bulb fluorescent shop-lights that
are 48" long, with 40 watts per bulb. If you have 2 of these over your
tank, you'll have 160 watts---nearly 3 watts per gallon. While you're
there, get 4 of the GE Plant and Aquarium bulbs and just use those..
Total cost for 4 bulbs and 2 fixtures should be under $40.

Good luck,
Wes