Oily film on surface

I’m noticing a bit of what I can only describe as a kind of oily film that forms on the surface of my 40g backup tank. Any thoughts? I run a small Tunze skimmer on it and one powerhead. I also run an airwand for gas exchange.

That’s pretty typical if you feed frozen foods. Do you have a surface skimming overflow?

I’m running this tank as an AIO. The Tunze Comline skimmer sits in the corner, my rocks provide biological filtration, aeration from the airwand, and I then the single powerhead–thinking of maybe getting an MP10 for it but we’ll see. Trying to keep this a bit more budget friendly. I have that AI single light on one side, but my plan is to get around to hanging that MarsAqua light I won in the club raffle a few months back. Just have to deal with drilling holes in the ceiling etc. Here’s a not so great pic:

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Ah, yep! When you have a traditional overflow with a weir (the teeth), it works to skim the muck off the water surface. That Tunze skimmer, I think, has a small overflow on it…right? One thing you can do to reduce the film is to point a powerhead at the surface to break it up.

Yeah, I notice that with the powerhead on the right side of the tank, the film sits on the left side. As long as it’s not a hazard I’m not too bothered. I don’t have a second powerhead (or an outlet for that matter) handy so I guess I’ll just live with it. Thanks for the help.

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Maybe try to aim the power head a little more to the surface to agitate more and keep it from building up?