Fish of all types are routinely sedated or anesthetized for transport, husbandry, diagnostics, medical and therapeutic procedures, or prior to euthanasia. Overdose of immersion anesthetic is a common method for fish euthanasia. Although eugenol has been shown to produce immobility in fish, the variation in concentration of active drug in clove oil makes sedation and anesthesia less predictable from a clinical standpoint. Propofol by immersion produces dose- and duration-dependent sedation and anesthesia in goldfish, koi carp and catfish. Anesthesia is accompanied by a decrease in heart rate and opercular rate, with some fish completely ceasing operculation. Propofol is used extensively as a sedative and anesthetic in human and veterinary medicine where it provides good muscle relaxation but no analgesia. Both propofol and alfaxalone can produce anesthesia in fish. Carbon dioxide can cause death at high doses or can be used as a sedative/anesthetic before a secondary means of euthanasia.