A fish farm having at least one land-based fish tank (1a-e) and a water supply system , the water supply system comprising: a supply line (2C,D) and a discharge line (2A,B), the supply and discharge lines (2A-D) being fluidly connected to a water reservoir ; a fluid intermediate storage ; a circulation conduit (9a-f) fluidly connected to the at least one fish tank (1a-e); a valve arrangement (10a-p) fluidly connected to the supply line (2C,D), the discharge line (2A,B), the fluid intermediate storage and the circulation conduit (9a-f), the valve arrangement (10a-p) having: a first operational configuration in which the valve arrangement (10a-p) permits circulation of fluid between the fluid intermediate storage and the at least one tank (1a-e) via the circulation conduit (9a-f); a second operational configuration in which the valve arrangement (10a-p) permits circulation of fluid between the fluid intermediate storage and the reservoir via the supply and discharge lines (2A-D) and; characterised by : a first valve unit (10a,b) fluidly connected to the discharge line (2A,B). the intermediate storage and the circulation conduit (9a-d); and a second valve unit (10c,d) fluidly connected to the supply line (2C,D), the intermediate storage and the circulation conduit (9a-d). a supply line (2C,D) and a discharge line (2A,B), the supply and discharge lines (2A-D) being fluidly connected to a water reservoir ; a fluid intermediate storage ; a circulation conduit (9a-f) fluidly connected to the at least one fish tank (1a-e); a valve arrangement (10a-p) fluidly connected to the supply line (2C,D), the discharge line (2A,B), the fluid intermediate storage and the circulation conduit (9a-f), the valve arrangement (10a-p) having: a first operational configuration in which the valve arrangement (10a-p) permits circulation of fluid between the fluid intermediate storage and the at least one tank (1a-e) via the circulation conduit (9a-f); a second operational configuration in which the valve arrangement (10a-p) permits circulation of fluid between the fluid intermediate storage and the reservoir via the supply and discharge lines (2A-D) and; characterised by : a first valve unit (10a,b) fluidly connected to the discharge line (2A,B). the intermediate storage and the circulation conduit (9a-d); and a second valve unit (10c,d) fluidly connected to the supply line (2C,D), the intermediate storage and the circulation conduit (9a-d). a first operational configuration in which the valve arrangement (10a-p) permits circulation of fluid between the fluid intermediate storage and the at least one tank (1a-e) via the circulation conduit (9a-f); a second operational configuration in which the valve arrangement (10a-p) permits circulation of fluid between the fluid intermediate storage and the reservoir via the supply and discharge lines (2A-D) and; characterised by : a first valve unit (10a,b) fluidly connected to the discharge line (2A,B). the intermediate storage and the circulation conduit (9a-d); and a second valve unit (10c,d) fluidly connected to the supply line (2C,D), the intermediate storage and the circulation conduit (9a-d). a first valve unit (10a,b) fluidly connected to the discharge line (2A,B). the intermediate storage and the circulation conduit (9a-d); and a second valve unit (10c,d) fluidly connected to the supply line (2C,D), the intermediate storage and the circulation conduit (9a-d). <EOS>