The tank is 30 inches long, and 21 inches high, per http://www.aqueonproducts.com/products/bow-front.htm
so you need a 24 or 30 inch long light. To get low light, with no CO2 needed, you need to find a light that will give you about 25-35 micromols of PAR at the substrate, which could be with the light sitting on top of the tank, or hanging above the top of the tank. If it sits on top of the tank, it would be about 19-20 inches from the top of a 2 inch layer of substrate. A single T8 bulb at that distance gives you about 10 micromols, so it would take 3 bulbs to get into the low light range. A 2 x 24 watt FishNeedIt, T5HO light would give you about 30 micromols at that distance, so that is probably the cheap way to go. Or a good quality T5HO one bulb light hanging about 10-12 inches above the top of the tank would also give you about that much PAR. That would cost a lot more.