Surface Film

[Aqua sobriquet]

I’m just starting an unheated and unfiltered 10L Nano. The only occupants until this evening was some Tetra Active Substrate and four Moss balls. I bought some Spider wood to put into the tank today and when I took the cover glass off I noticed quite a bit of surface film. I’m sure the culprit must be the substrate as the Moss ball were happily sitting in a vase for a week without any problems. Anyone had this problem before? I did thoroughly rinse the substrate with hot water before putting it in.

 

[Simon Cole]

Yes this is very common in new and old tanks. It is almost guaranteed without flow. There is a dusty green algae that likes to form a film. You can also get patchy-shiny and sticky bacterial films. At the moment I have a dusty film in one of my tanks, but I wouldn't like to guess at the cause. It's all quite natural. Drop a clean paper towel on the surface and lift it away from the centre, or get a skimmer. Some people will say this is due to the chemical balance, but really many natural systems are unbalanced and work in cycles. I would not look at this as something that should be controlled. Daphnia, or even better cyclops, would be a very sensible livestock choice. Alternatively, a paramecium strain might work if you can identify the microbial cause. Less common are scums and chemical films. They are surprisingly common in limestone fenland springs and in glacial melt-water.