I went and took a look at my friends 20 gallon and it doesnt seem like its long enough. the dimensions are 12"L x 14"W x 17"H

With the skimmer needing 8" x 7" footprint, it doesnt seem it would leave much room for the refg. and return chamber.

I was thinking maybe 36" L would be just short enough for me to jimmy it into the stand and give me enough room to fit everything in the sump.

I saw a 950 gph Danner Mag-drive pump for $75. Are these good pumps? It sounds like they would be quiet because its magentic and it has a 3 year warranty.

When you say a closed loop manifold you mean using PVC plumbing down into the sump instead of using hoses to and from the tank?

Thanks!!