Which is a common aquatic pest target for algaecides?

• A. Crayfish.
• B. Water fleas.
• C. Algae (e.g., pond scums, filamentous algae).
• D. Mosquito larvae.

Answer: (C)

Algae are the target because algaecides are products designed to suppress photosynthetic aquatic organisms that form visible growths like pond scums and filamentous clumps. Controlling this algae helps keep water clear and helps maintain oxygen levels and light penetration for other aquatic life. The other items listed are animals, not algae, so they require different types of pesticides or control methods (insecticides or larvicides for mosquito larvae, and other measures for crustaceans like crayfish or zooplankton like water fleas).