This dataset contains information about water conditions at Tatton Mere and Rostherne Mere, Cheshire over Summer 2022. Data was collected weekly as part of a study into the presence of algal blooms and the toxins they may produce. In situ testing recorded temperature, pH, oxygen and conductivity measures. Water samples were also collected and analysed in the laboratory for anion, cation and metal concentrations, chlorophyll-a concentrations and cyanobacteria identification and counts. The work was supported by the Natural Environment Research Council (Grant NE/X011607/1). Full details about this dataset can be found at https://doi.org/10.5285/3fcb8359-9ca3-4319-b680-e0286f59571a