Pond Boss Forums GENERAL QUESTIONS Help Surface Film ?

Have a 1/5acre pond in NC. Pond is ten yrs old but our first fall in the house. Last couple weeks a surface film has appeared that resembles pollen in the spring time, but it's not spring. Is it common to get this surface film at this time of year? Pond is in a heavily wooded area and has lots of leaves that fall and sink in the pond.
Just curious if others have experienced the same.

A high amount of organic material can favor some algae species that will form surface films of various hues depending on the algal specie. Season, day length and water temperature will influence when certain species develop. Nutrient concentrations influence the size of the "bloom".

Thanks Bill.
Periodically we see some small areas with surface film that shimmers as though it is some type of oil. Is it necessarily an outside contaminant such as motor oil, or is there something more natural that might be produced from the pond's environment?

Thanks for any input you might have.

It is a type of algae, usually cyanobacteria (blue-green algae). It will change colors as it starts, grows, and starts to die off. At times it will look just like an oil slick from motor oil. Usually it is not a problem, but it is safest not to swim in it, or to let the dog drink from the pond.

There is a lot of information and photos on the Internet regarding blue-green algae.

Ken

Thanks. That blue-green sounds bad. Currently I don't have aeration but quickly coming to realize it would be best.
Will better aeration help to abate the growth of this type algae?

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.

Thanks for the information. Definitely planning on an aeration system as soon as I can wade through the maze of information available.