Fleet Pond is a Site of Special Scientific Interest and Hampshire's largest freshwater lake. A major partnership project 10 years ago successfully improved some key elements of the lake's water quality, but it continues to suffer serious algal blooms. This short video looks at the most common cause of algal blooms - over enrichment of lake water with nutrients such as nitrogen and phosphorus and the role of urban runoff and drain misconnections entering the Brookly Stream - one of the two inflow streams.
https://www.youtube.com/watch?v=ZN7pRu7f7Ms
Prompt reporting of suspected sewage or wastewater pollutions of the stream will help reduce damage to the environment. Thames Water's emergency number is 0800 316 9800