See I told you so!?!?!? Opinions needed.

[Samw]

Its not the sump that will fix your surface scum problem. I have a sump and also have a surface scum problem. The reason is because my water return is below the water surface. To fix the surface scum problem, I added an aquaclear 200. The water from the filter is returned above the water line which breaks the water surface and prevents surface scum from forming. You don't really need an aquaclear if you have a powerhead or something set up close to the surface such that it can produce a lot of crashing waves. If you want to set up a sump, you can but you still need to place the water return above the water surface in order to prevent the surface scum from forming.

Having said that, you have an AquaC Remora which should have helped with the surface scum. I guess its because the water that is being returned is going into the prefilter box which prevents the water surface of the rest of the tank from breaking.