how the beep beep beep do i get rid of an oil slick at top of tank

[Milad]

Originally Posted by golf nut

This is 100% correct, I have seen way too many tanks with oils slick syndrome, always have the surface water move to the overflow box.

The foam in the overflow box doesn't sound quite right either, is it falling for quite a drop after going over the overflow? sounds like the overflow is acting as a skimmer.

there is no initial drop in the overflow box

Im coming up with a design to put the returns on the opposite side of the tank as we speak (or type). Its probably going to be on top of my light fixture so it wont be seen.