Our tanks are very shallow, so even though the light is T8, it produces medium light near the bottom and high light near the top. The light is only a couple of inches away from the tops of your plants. I think that has something to do with it. Hoppy has a great chart on a sticky in the lighting forum.
Hoppy's Par Chart
Also, you mentioned the background. I found that I could slip the plastic backgrounds they sell at the LFS up under the plastic rim and then tuck it between the "glass" and the plastic base. It made it easy to hold it in place, and then I just taped it down in a few spots. I thought about trying the mineral oil trick to make it appear more black, but I think it looks OK for now.