Which chemical is commonly used in pools to keep algae growth under control?

Chlorine is widely recognized as the primary chemical used in swimming pools to maintain water sanitation and control algae growth. Its effectiveness as a disinfectant is due to its ability to kill bacteria, viruses, and other pathogens, while also inhibiting the growth of algae. When chlorine is added to pool water, it forms hypochlorous acid, which actively works to sanitize the water.

Chlorine serves a dual purpose; it not only eliminates algae but also helps in preventing its growth by ensuring that the water chemistry remains balanced. Regular testing and maintenance of chlorine levels are essential to keep pools clear and free from unwanted algae blooms.

Other chemicals mentioned in the choices do serve specific functions in different contexts but are not standard treatments for algae control in pools. For example, calcium hypochlorite is a form of chlorine used for chlorination, and while it contributes to sanitization, it is essentially a type of chlorine rather than a standalone agent specifically employed to control algae. Aldicarb and permethrin are pesticides and insecticides, respectively, and are not suitable for swimming pool treatment.