Mike, the surface scum was exactly why I went with a AIO design with my 5.5g. I partitioned off about 4" off one side with acrylic and made two chambers. Cut teeth in one side for the overflow and the other side is the return Minijet. No surface scum.
I really need to glue down the corals I've raided from my 30g tank and purchased at the LFS. Right now I have xenia, star polyps, clove polyps, two colors of candy cane, a red mushroom and a neon green yuma. The sole fishy is a neon goby. The CUC is rounded out with three tongan nass snails, a turbo snail, three banded trochus and two hermits.
Still wating for $$ to magically appear so I can get the T5 fixture over it. Right now it has my old 2x18w PC fixture from my 2.5g tank sitting on it.
When you get a chance, an updated pic would be great!