___ is a chemical used to control algae.

• A. Sodium Bicarbonate
• B. Sodium Chloride
• C. Calcium Carbonate
• D. Copper Sulfate

Answer: (D)

Algae control relies on substances that are toxic to algae or disrupt their growth. Copper sulfate releases copper ions that interfere with essential enzymes and the photosynthetic process in many algal species, stopping growth and causing cell death. This makes it an effective algaecide for water where algae need to be controlled. The other chemicals listed don’t act as direct algicides; sodium bicarbonate mainly adjusts alkalinity, sodium chloride adds salt, and calcium carbonate affects hardness and buffering. They influence water chemistry but don’t kill algae at typical usage levels. Remember that copper can be toxic to fish and other aquatic life, so it must be used carefully according to directions.