Also known as eugenol, clove oil is a sedative at low doses, but at higher doses it has been recommended by some researchers as an inexpensive way to euthanize fish, particularly small fish. In a container, mix aquarium water with clove oil and mix. When exposed to high concentrations of clove oil, fish quickly lose consciousness and stop breathing, both of which reduce pain. Hypoxia eventually causes death, and once verified, the fish can be removed from the water and clove oil mixture. The required dose for euthanasia is 400 mg/l or more.
Clove oil contains some substances believed to be carcinogenic and should be handled with care.