film at top of water

[golf nut]

I assume "the top of my water" means on the surface of the tank, try pointing the returns from the sump down the back of the tank to encourage the surface water to move towards the overflow box.

[Marlin65]

Not enough flow if it is your main tank. Add some power heads and they should take care of that.

[reefmutt]

that film usually indicates an excess of nutrients in the water...It could be protein buildup or a fine algae layer.
adding some carbon and/or phosphate remover, and/or protein skimming as well as doing water changes will also help get rid of it.

[Snaz]

Reduce the height of the overflow weirs so the water flows out truly from the surface and not from just under the surface.