Scum On Surface

[SexyFishKeeper]

So over the past two weeks, a sort of oily scum has formed on the surface of the water. When it breaks up it doesn't go back as it's like rather solid.

The other night I removed all (or nearly all) of it by placing paper towels on the surface.

However, today it's returned after 3 days.

Its so solid that it keeps my CO2 bubbles underneath it.

Any ideas?

180 Juwel Vision
19 Harlequin Rasboras
5 Ottos

Dose Dry Ferts:
Macro (Mon, Wed, Fri): KNO3 2.3g, KPO4 0.4g, MgSO4 3.4g
Tue, Thur: Trace 0.5g
Daily: 7.5mls of Easy Carbo

50% water change on a Monday.

Pointing the filter outlet up more to cause more ripple doesn't solve it.

 

[Colin_T]

It could be a build up of nutrients and proteins from the fish food or fertiliser. More surface turbulence should help break it up and water changes should also help. However, if you are using CO2 then more surface turbulence will get rid of this making it a waste of time. Perhaps do another water change but don't add any more fertiliser for a few days and see if it helps. Have an air pump come on at night so the air bubbles can break the surface tension up and help get rid of the scum.

 

[backtotropical]

You could also try feeding a different food for a while.

 

[DiscusKeeper403]

My guess would be lack of surface agitation.