Pond Boss Forums GENERAL QUESTIONS Help Surface Film ?

If the algae surface film is a bluegreen (Cyanobacteria) the cause is likely a nutrient balance issue. Aeration may help rearrange the nutrient balance in the pond. Regular pond bacterial or microbe applications may help with leaf decay and nutrient concentrations to favor a better type of algae. The excessive tree leaves that get in the pond is likely the real source of the problem algae film.

Ideally your first step is to determine if it is Cyanobacteria or some other species. One easy way to determine if it is Cyano is to collect a good amount of the film and some surface water to 2/3 fill a jar or bottle. Cap it, then 3-4 hrs later, uncap and smell the air above the water in the jar. If it smells offensive like moldy, vile or disgusting then almost positively it is Cyanobacteria. Mild odor, fishy smell, or almost no odor is another group of algae and of little concern since it should soon dissipate as winter progresses.

If the algae is bluegreen then to remove it use some diluted liquid Cutrine-Plus, similar buffered copper based algaecide both diluted according to label, or a light dose of copper sulfate (1/2cup dissolved into 3-4 gallons of water) and spray the surface film after a gentle breeze has pushed most of the film onto one end of the pond.

All ponds that receive significant organic inputs should be aerated to maintain as good as possible water quality in a pond that is basically an "aquatic compost pile" due to large amounts of annual leaf inputs which accelerates the pond aging process.