You could use an egg crate cage to keep the macro from your pumps and skimmer. I have macro under 2x18 w T-8s and it is growing well. I don't think that you need a ton of light. I think that a lot of people are using a flourscent spot light from lowes.

I have a 55w PC light that would work well if you want it for $15, and I will give you come cheato. Great stuff because it doesn't need sand and grows super fast.