I don't see the big deal about growing a plant in the tank. I agree that it's not the best planting site, but I think you can grow a healthy plant. I think you will need to cover the exterior glass with a thick light proof cloth to keep light from the roots and heat to the soil. The cloth will cost you no more than a dollar or two at a store like Wal-Mart. You can attach velcro around the tank and to the cloth if you want to see when you water for a few more dollars. Water slowly and stop at the bottom. You need to avoid a soggy bottom.
Use a soil mixture that will allow the roots to get some decent air.

I happen to be growing in an icebox right now. Even though I have the drain plug open, I have yet to see any excess drainage and I already started flowering. I'm not sure why you're choosing to grow in a tank but if that's you goal, go for it.:jointsmile:
You can try two small plants or one larger one.