Wierd film on top water of tank?

Are you running diy co2?

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Normally I would say biofilm but your description of "thick white stringy" sounds a bit odd. Unless it is just being pushed by the current to one area and smooshing onto itself.

Run an air stone for a spell to create more surface movement to break it up. I normally run one at night. If I don't run it for a few days, I get the film on top as well.

I also vote for biofilm or surface scum as well. Good filter or aeration usually removes it for me.

had a similar issue in my tank. I added sand and had a water pump below the water line and it was instant funk, added a HOB filter for surface movement... Bam, funk gone...

Though your description sounds like a DIY co2 issue.

Place a jet just below the surface for surface agitation? Add a carbon layer to the filter?

The above also removed oils from the surface.

I've found a skimmer to be too big for my 10 gallon and my AquaClear20 was not strong enough to pull the skimmer but maybe you might have better result with a more powerful filter. Also skimmer defeats the purpose of a silent setup IMO.