Green water is usually a condition within the pond water’s chemistry that is out of balance, typically caused by nitrates. The good news is that green water is not harmful to fish, but it looks terrible. A quick fix for green water is to use a pond sterilizer to clear the water, the long term fix is to ensure proper filtration is installed; feeding habits are kept in check, and a good mix of pond plants are in your water garden. For further discussion please give us a call.