Betta water?

[AtoZ Cichlids]

I have seen tons of cases with bettas where the surface of the water looks cloudy and oily. I read somewhere years ago that its from the betta but I dont remember what it is or how to rid of it. Does anybody know why they do that and how to get rid of it in bowls? Even with 25% water changes every 2 days it doesnt seem to go away. I dont think that it comes back but rather it just stays there with water changes. This leads me to think that its in the water not just on the surface.

 

[Mebbid]

It's a bio film. It forms on the surface of almost all tanks but you never notice it because there is soo much surface agitation in tanks. The reason you see it soo often in betta tanks is because they are kept in completely unsuitable conditions such as too small of a container with little to no water flow.