Film on waters surface. Why?

[regina filange]

Hi!
I have a 12 gal Auqapod. When I purchased this unit, it said that it "skimmed" the surface so you didn't have "oil slicks" on the surface. Well, clearly this isn't working like it should.
I do a 2 gal water change once a week, yet i still have this problem.
Should I worry about this? What is it caused from? What can I do to stop this?
Thanks!

 

[subielover]

Hopefully you have an additional powerhead in the tank besides just the return. Aim one of them at the surface of the water, this will break the film and allow oxygen exhange.

 

[regina filange]

Ok. I'll give it a try and see what happens. Thanks for your help!