Green pond water is typically caused by an excessive amount of suspended single-celled algae. These microscopic algae turn the water green and can make it difficult to see fish or the bottom of the pond.
Green water is different from string algae, which grows attached to rocks, waterfalls, and other surfaces.
What causes green pond water?
Common contributing factors include:
- Excess nutrients from fish waste, uneaten food, or decomposing debris.
- Too much direct sunlight.
- Inadequate biological filtration.
- Excess nutrients entering the pond through runoff.
How do I clear green pond water?
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Use UV clarification.
- Install an Aquascape UltraKlear UV Clarifier or UltraKlean Pond Filter with UV clarification.
- UV light targets suspended single-celled algae as pond water circulates through the unit.
- Ensure the equipment is properly sized for the pond and water flow.
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Maintain proper filtration.
- Remove accumulated debris from the skimmer.
- Clean mechanical filter media as needed.
- Verify that water is flowing properly through the filtration system.
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Reduce excess nutrients.
- Remove decaying leaves and accumulated organic waste.
- Avoid overfeeding fish.
- Use Aquascape Beneficial Bacteria according to product directions to support biological filtration.
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Improve the pond's natural balance.
- Add appropriate aquatic plants to help absorb available nutrients.
- Provide shade where practical to reduce excessive sunlight.
- Maintain adequate circulation and aeration.
What if the pond water stays green?
- Verify that the UV clarifier is operating.
- Inspect the UV bulb and replace it when required by the equipment instructions.
- Check for reduced flow through the filtration system.
- Confirm that the UV equipment is appropriately sized.
Important: Treatments designed for attached string algae are not necessarily effective against suspended green-water algae. UV clarification is the preferred approach for green water.