algaecide
/ˈæl.dʒə.saɪd/
noun
- A substance used to kill or control algae, especially in ponds, pools, or water tanks.
- Some algaecides are safe for fish, but others can harm them.
- We added algaecide to the swimming pool to keep the water clear.
- The pond owner used an algaecide to stop the green slime from spreading.