Answer
How do I stop my pond turning green?
Balance, not chemicals: planting, filtration, circulation and shade starve the algae.
In short
Green water is algae, fed by too many nutrients and too much light. The lasting fix is balance, not chemicals: enough planting to compete with the algae, the right filtration and circulation, some shade, and not overfeeding fish. A balanced ecosystem pond stays clear because the biology does the work.
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