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Algae in your garden pond can transform from a pleasant green to a real nuisance. In this article, you’ll discover what algae are, why they might overrun your pond, and how you can naturally keep them under control. 

What Exactly Are Algae? 

Algae macro shot
image: Chokniti Khongchum –

Algae are simple, often green organisms that thrive in water-rich environments. They conduct photosynthesis, similar to plants, and are an essential part of many aquatic ecosystems. In your pond, they play a crucial role in oxygen exchange and can help keep the water clear. 

Why Do Algae Sometimes Overgrow? 

Several factors can cause algae to suddenly proliferate in your pond, including: 

  • Excessive nutrients in the water, often due to leftover fish food or decaying plants. 
  • An abundance of sunlight, which promotes algae growth. 
  • Insufficient water circulation, allowing algae to spread rapidly. 

Possible Solutions for Algae Problems 

Frog in a pond surrounded by aquatic plants
image: Prayer Turambi –
  • Plants as Natural Competitors: Aquatic plants compete with algae for nutrients and light. A well-planted pond can therefore naturally limit algae growth. Suitable plants include water lilies, duckweed, or marsh marigolds. 
  • Mechanical Removal: For a small amount of algae, regular removal with a net or pond brush can be effective. For severe infestations, completely renewing the pond water is the most effective combat method. 
  • Fish and Animals: Certain fish species, like goldfish or koi, as well as some types of pond snails, feed on algae and can help control it. 
  • Pond Filters: A well-functioning pond filter helps keep the water clean and low in nutrients, hindering algae growth. 
  • “Inoculating” Water: To combat algae in your pond, consider using water from another healthy pond. You can obtain about 10 to 15 liters of water from a friend or neighbor’s well-functioning pond system. Adding this water to your algae-infested pond can introduce microorganisms that start fighting against the algae. 

Tips for Prevention

  • Regular Pond Maintenance: Keep your pond clean by regularly removing dead organic material like leaves and dead plant parts. 
  • Balanced Feeding: Avoid excess food, as it serves as a nutrient source for algae. 
  • Monitor Water Quality: Regular water quality tests can help detect imbalances early. 
  • Create Shade: Excessive direct sunlight promotes algae growth. Some shade-providing plants or partial covering can be beneficial. 


Algae are a natural part of your garden pond’s ecosystem. However, an overgrowth can disrupt the biological balance. With the right measures and regular maintenance, you can keep your pond balanced and prevent excessive algae growth. Remember, every change in the pond affects the entire ecosystem. A balanced ratio of plants, animals, and good water quality is key to a healthy pond. With patience and care, your pond will not only be a beautiful but also a vibrant part of your garden. 



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