The 4 Stages of Azolla: Identification and Treatment Guide

Q. Our dam has been overtaken by Azolla, can you recommend how we treat this and prevent it from coming back?


Azolla, a free-floating aquatic fern, can transform your water body into a weed-infested nightmare if left unchecked. This seemingly innocuous plant, known scientifically as Azolla filiculoides, is a versatile species that can rapidly take over water surfaces. In this Q&A, we will explore the four growth stages of Azolla, how to identify them, and the most effective treatments to keep your aquatic oasis in check

  • Stage 1: Primary Growth – The Beginning – In this initial stage, Azolla plants are scattered across the water’s surface flat and there is an abundance of free water. During this phase, Azolla covers around 0-30% of the water body.
  • Stage 2: Secondary Growth – A Splash of Colour – As Azolla continues to thrive, it becomes more noticeable. The water’s surface will display hues of red, green, or a combination of both. At this stage, Azolla covers approximately 30-60% of the water body.
  • Stage 3: Tertiary Growth – The Total Takeover – By this stage, Azolla has infested the water body, leaving no visible water. Its colours, red, green, or a mix, dominate the surface. Azolla’s presence has reached 60-100%,
  • Stage 4: Multilayered Growth – The Ultimate Challenge – In the fourth and final stage, Azolla has completely covered the water body. Multilayered weed mats form, with ridge-like thickenings as layers build up.

Treatment Strategies for Azolla Management

Now that we’ve identified the growth stages let’s look at treatment options for effective Azolla control:

How to Apply Treatments:

  • AQ200 + Wetting Agent: For all stages. For 100% coverage, consider thinning out Azolla before applying the herbicide. Check hidden areas beneath rocks, lily pads, and reeds for any remaining plants, and spot treat them for optimal results.
  • Orange Oil Treatment: For Primary and Secondary stages. Partially remove sections of the infestation to create space for the treated matter to sink. Apply an extra 20% of the product for saturation. Multiple light applications over several days give the best results.
  • Azolla Skimmer Use: Azolla Skimmer: For all stages. This method works best when used alongside spray treatments, enhancing your weed control efforts.

Controlling Phosphorus for Water Health

Azolla can thrive in nutrient-rich waters, particularly those with abundant phosphorus. Understanding how phosphorus enters your water is crucial for prevention:

Sources of Phosphorus:

Fertilizers, runoff, erosion, sewage, organic matter decomposition, natural weathering, and bushfires.

Managing Phosphorus:

  • Limit runoff: Minimize runoff by implementing proper drainage systems for improved water quality.
  • Reduce fertilizer use: Use fertilizers sparingly and according to recommended guidelines, reducing the risk of excessive phosphorus in your water body.
  • Prevent topsoil erosion: Implement erosion control measures to keep topsoil from entering the water, preserving its quality.
  • Manure handling: Properly handle and manage animal manure to prevent phosphorus runoff, ensuring the health of your water body.
  • Soil conservation practices: Adopt soil conservation practices to protect water quality, controlling phosphorus levels effectively.
  • Wetland and riparian buffer restoration: Restore wetlands and create riparian buffers to naturally filter phosphorus from the water, promoting a balanced aquatic ecosystem.

Removing Phosphorus for Water Body Health

  • Aeration: Promote oxygenation in your water body to reduce phosphorus levels, enhancing the overall health of your aquatic oasis.
  • Phoslock and Phosflow: Consider these treatments to effectively reduce phosphorus concentrations, contributing to a healthier and more vibrant water environment.

by Aquatic Technologies
If you have any questions regarding looking after your dam or pond and what products are the most suitable for your situation, please read through the helpful articles on our site or feel free to contact our friendly team who can help you maintain proper health in your water body year round.
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