Filter creating foamy bubbles

[ltkaarina]

Hi all!
A few days back my sponge filter started making this foamy sheet of bubbles on the surface and I have no idea what could be causing it?

I completely reworked the aquarium around when it started (added some more gravel and hardscape, replanted all plants), but since then I have cleared out any decaying plants, did a 50% water change yesterday and cleaned the filter but that's had no effect.
No soap or any medication has been used or added to the water either.

Any help would be appreciated!

 

[Uberhoust]

Doesn't look that bad. The water surface appears to have a bit of the surface scum, perhaps a protein scum. It is more common in setups a bit older. I would try and scoop some of the surface water away, or take a paper towel and lay it on the surface then remove it to remove the scum. I would likely do a water change as well.

If this is common you might want to look at increasing the surface agitation so that the scum is broken up and enters the water column where it can be filtered, but I would also look at how much you are feeding the fish, perhaps you are feeding them a bit heavy.