I had a similar issue on the surface of my sump, if there is so surface agitation a film begins to form. I solved this by adding a powerhead pointed towards the surface to stir the water. You could also probably use some sort of surface skimmer as well. The powerhead is probably the easiest fix.
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- 33 Gal - 20Gal Sump, MP10/Hydor Powerheads, Aquaticlife 4x T-5HO, Vertex IN100, TLF w/Biopellets, Tunze ATO
-45GAL Build in Progress!-
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