This comes down to how much money do you want to spend?
If you don't mind spending the money, replace the hood with a glass canopy, and get a 2 bulb T5 or T5HO that clips to the rim of the tank. They usually come with standoffs to keep the light a couple of inches off the tank.
At the other end of the cost spectrum is doing what Bonswani mentioned, use CLF bulbs. Since you has an existing fluorescent fixture, you would need to retrofit it for standard CFL bulbs, or get a cheep incandescent fixture and screw the CFLs into that.
Other alternatives would be to get one or two T5 retrofit kits, gut the existing fixture and install them.
All of the methods will work, but consider how good you are with DIY projects, and electrical wiring.