There are a few different routes you can go. It looks like a 55G tank, so I'm going to assume that is what it is, please correct me if I'm wrong.
Depending on where you live, you may be able to find a used fixture to save you some money.
There are T5 fixtures, you'd need a 6 or 8 bulb fixture, preferably with individual reflectors. Ex: AquaticLife 48" Six bulb fixture.
There are metal halides. A good 4ft unit with 2 150 watt halides would work. Coralife makes some decent units, the AquaLight model is very good. These are usually the easiest to find and the cheaper option to T5s.
There are LED fixtures. These are more expensive upfront, but do save in the long run, because bulbs don't need to be replaced nearly as often. They also don't use as much electricity or produce as much heat. There are premade fixtures such as Aqua Illuminations SOL or Acan Lighting, or there are DIY fixtures, which are much cheaper if you're handy. Don't waste your time looking at the MarineLand fixtures, they're garbage.
