Hair algae tend to grow rapidly in spring and autumn due to suitable light and nutrient-poor water. The key to control is shading + biological competition; avoid chemical treatments.
Three-Step Approach
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Emergency Removal: Manually or with tools, clear dense algae clusters, focusing on bottom drains and filter inlets.
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Quick Shading: Cover about one-third of the water surface with shade cloth for 5–7 days.
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Biological Competition: Add chlorella solution (100 ml per ton of water) to reduce light availability for hair algae.
Long-Term Prevention
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Maintain 20%–30% surface coverage with floating plants (e.g., duckweed) for shading.
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Feed moderately to increase water fertility and alter conditions for algae growth.
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Introduce algae-eating organisms such as black-shell shrimp (15–20 per ton of water) for cleanup.
Important Notes
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Do not use chemical algaecides, as they can harm koi and the nitrogen cycle.
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Avoid completely removing all algae; retain a small amount to help maintain ecological balance.
Core Principle: Gently regulate light and nutrients to encourage beneficial algae and plants that naturally suppress hair algae, ensuring both clear water and healthy koi.
