TedJ - Thin "mild" surface algae films are usually harmless; more visually offensive than harmful to fish and other aquatic life. Thick surface films can be bluegreen algae their affects are debatable. The type of species causing the bloom will determine its impact on the overall pond. It is often a case by case basis.

Cutrine Plus (liquid) based spray will kill most of the algae in the surface film especially when it is pushed to one end or side by a gentle breeze.

pat - about cleaning it up. When it dies, either naturally or due to treatment, it will sink to the bottom and decompose. Nuisance algae blooms give one a small idea of how productive a nutrient enriched pond can be.

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management