Pond Boss Forums INTRO Questions & Observations Algae issue:

I have seen similar small surface scums or films caused by Euglena types of algae. Euglena types are not harmful and usually grow well in water with high amounts of dissolved organic compounds sometimes caused by feeding lots of fish food. Sometimes they are temporary and disappear when the dissolved organics concentration subsides. To test if it is Euglena collect some of it in a water or soda bottle 2/3 to 3/4 full. Cap it. Allow to sit for a few hours then uncap and smell the air in the bottle. It it has strong offensive / vile odor it is bluegreen algae (aka Cyanobacteria).