[rzn7z7]

Yeah, I get a surface film on my established tank from time-to-time, too, and from what I can tell it comes leftover from fish food, excessive organics in the water column, decaying leaves, etc. Solutions include more frequent water changes and filter cleaning, increased surface agitation (for better O2), purigen, and surface skimmers (I have an eheim)

A search here on the forums turned up a lot of hits on this topic