Which of the following is a common method for controlling pool algae?

Using algaecide treatments is a well-established approach for controlling pool algae. Algaecides are chemical agents specifically designed to prevent the growth and reproduction of algae in swimming pools. These treatments work by targeting the biological processes that allow algae to thrive, thus keeping the water clear and clean. When applied correctly and in accordance with the manufacturer's instructions, algaecides can effectively eliminate existing algae and prevent future outbreaks, especially in conjunction with proper sanitation and circulation practices.

The other methods, such as raising pH levels or reducing circulation, would not effectively address algae problems. Higher pH levels can actually encourage algae growth, while reduced circulation can create stagnant areas where algae can proliferate. Similarly, decreasing chlorine levels compromises the pool's sanitation, allowing algae to grow unchecked. Therefore, the use of algaecide treatments stands out as the most effective and proactive method for algae control in swimming pools.