Persistent biofilm

[bristleworm]

What type of overflow do you have? Is this an AIO system?

 

[DmitryB]

If your picture is your surface agitation, to me thats not much agitation. The surface of my tanks looks like white water rapids, that may be overkill but you should at least have some strong ripples going across the surface, I like to see the occasional tiny bubble enter the water from the amount of agitation.

You need more surface agitation to mix that stuff back into the water so that your filtration can filter it out. Move your powerheads to just a few inches below the water and aim them up.

The surface film cuts the light and also cuts the gas exchange (cutting the oxygen level), as well as it is unattractive, so its important to get it resolved.

Does strong surface agitation create water micro bubbles that then float through the tank?