1) Chemical used to kill fish 
A piscicide is a chemical substance which is poisonous to fish. The primary use for piscicides is to eliminate a dominant species of fish in a body of water, as the first step in attempting to populate the body of water with a different fish. They are also used to combat parasitic and invasive species of fish. Examples of piscicides include roteno...
substance that kills fish
Substance intended to kill fish.
Chemical used to kill fish.
piscicide A substance poisonous to fish; thus, killing fish (fish killer).