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What's in My Pond? Filamentous Algae

Writer: Wesley Gerrin
Wesley Gerrin
Aug 21
2 min read
Green algae on the surface of a pond.

WHAT IS FILAMENTOUS ALGAE?

IDENTIFICATION

Identifying a plant as filamentous algae can be as simple as picking it up. It does not have leaves, roots or stems like vascular plants. Instead, you will only see an intertwined system of strands that will often feel like hair or wool. Some species of filamentous algae are more of a problem than others, so it is important to definitively identify the algae before attempting to manage it. Identifying filamentous algal species requires a microscope and can be difficult without specialized training or experience.

LIFE CYCLE

Understanding life cycles is critical to managing any species. Most people don't see filamentous algae until it forms surface mats, leading some to a misconception that its entire life cycle happens on the surface. However, nuisance filamentous algae commonly begin growing on or near the bottom. As the bottom mats become thicker, they trap oxygen bubbles underneath them. Once enough oxygen builds up, the mats float to the surface. Like other plants, filamentous algae require nutrients, sunlight, and suitable water temperatures to start their life cycle at the bottom.


Infographic showing algae starting to grow on the bottom of a pond, the growth becoming more dense, accumulating oxygen bubbles beneath the mat, then floating to the surface of a pond.

BREAKING THE CYCLE

Because surface mats are often the only visible part of the filamentous algae life cycle, bottom mats are often overlooked and are not addressed by algaecide

treatments. For this reason, treating surface mats with algaecides frequently leads to a cycle where surface mats are killed and replaced by new mats from the bottom soon after the treatment. This cycle can be frustrating and expensive. The best way to break this cycle is to not only address the algae mats you can see, but also prevent the bottom mats from growing in the first place.

MANAGEMENT

The best way to manage filamentous algae is by being proactive, rather than reactive. Our management solutions always involve multiple integrated strategies aimed at disrupting the filamentous algae life cycle at all levels.


  • Remove surface mats

  • Decrease sunlight penetration to the bottom

  • Mitigate sources of nutrients

  • Reduce the amount of decomposing organic material reaching the bottom


Need Help with Filamentous Algae?



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