Natural Approaches to Reducing Pond Algae

starting to pull the skimmer across the pond

Keeping a pond clean & clear is no easy task in the face of an algal bloom. Oftentimes, there is a combination of factors contributing to the proliferation of these plant colonies: excess nutrients; a calm, stagnant surface; a lack of new water to replace the old; warm temperatures; and abundant sunlight. An algal bloom can develop with staggering speed when these factors overlap. 

While chemical algicides and pond dyes are available, they have unseen costs to the surrounding ecosystem. At the farm we prefer to take a more natural approach. Three years ago we implemented an annual program using loose straw packed into cages to facilitate the development of natural compounds called algistats. While we have mixed results over years, even switching to barley straw, we overall still see the benefits of the natural approach. Where algicides kill algae at a great cost to the aquatic ecosystem, algistats are often naturally-occurring and prevent the growth of new algae. They do not pose risks to the fish, reptiles, amphibians, plants, and single-celled organisms of the pond. 

This year, likely due to a combination of factors, we have had a larger algal bloom than usual, and we have needed to manually remove the thick mats of algae before they break down. If this were to happen, the process would sap oxygen from the water and leave little to none for the plants and animals who so rely on clean, oxygenated water to thrive. 

We quickly made a skimmer with reclaimed parts from the shop and secured them with zip ties. This skimmer has already proven to be a great success. It can be dropped in the water at a given starting point, then we throw the rope (with a weight on the end) along the pond edge to another accessible area and walk around to retrieve the rope, then pull the skimmer all the way to that edge. With the skimmer, we can collect a tremendous amount of algae within an hour. Using this new system, we’ve been able to keep our aquatic creatures happy and healthy in clean, oxygenated water - without any chemical algicides.

tossing the farm-made skimmer into the pond

One last item of note for anyone considering this effort for their own pond; the removed algae makes for a terrific compost addition! We suggest allowing the removed algae to drain its water back into the pond overnight, then collecting the dried proceeds in the days that follow. Mix the dried algae into the compost, and it will contribute macro - and micronutrients, as well as water retention qualities and humus. 

a clear pond!

If you are interested in learning more, feel free to reach out! farm@harlemvalleyhomestead.com.