You could grow some plants as others have said, but they're not going to ever be as nice as someone with a proper lighting setup. I agree with Adrian about the Sunblaster, or even an old 4' Coralife NO t5 setup would be good.
36" on a 48" tank means you'll have trouble growing anything in a the 12" with no light (or very low light I guess). As long as you're ok with that and the weird light pattern it's not a problem.But wait I'm pretty sure there was also a couple [email protected] I think bit there only 36" does that change anything if I do diy lid