Pond Boss Forums AQUATIC VEGETATION Identifying plants Algae or pollen?

Often an alum tretment will not cause all plankton to be completely removed from the water column. Alum treatment can strip out some dissolved phosphorus from the water column. Nutrients still present after an alum treatment will stimulate an algae bloom.

Film on pond in morning during a bloom will usually be one or a combination of several things. One would not know for sure unless it was exmined microscopically. It could be as ewest says but since it has color then I suspect it is living algae that moved to the surface at night seeking more light. Waves or activity will mix it below the surface until things are calm again and it moves back to the surface. When the bloom subsides the film will almost always dissappear. Various types of air pollution will settle on the pond and can cause films often grayish ones. Surface films occur most frequently in warmest months when winds are least.