Abstract: A non-chemical device and method prevents the growth of algae in a cooling tower basin. Cooling tower basins can experience algae growth when exposed to sunlight. This algae growth is typically controlled with chemicals (algaecides). Based on the chemical composition of the algaecides, adverse and/or counter-productive reactions may be experienced, resulting in adverse and/or counter-productive consequences. Further, algaecides are toxic and may be discharged into sanitary waste streams when treated cooling tower water is released. In addition, when algaecide treatment levels fall below effective levels, algae will return, requiring on-going dosing of algaecide into the cooling tower water to maintain control of algae. The device can create a block to prevent sunlight from reaching the cooling tower basin water. Since algae growth requires sunlight, by blocking the sunlight, algae growth can be prevented.