We know in our hearts when it is time to say goodbye to an ailing animal — when the quality of life is not quality at all. Many people feel the same emotions when losing a pet koi or goldfish as they feel when they lose a furry pet such as a cat or dog — to a more or lesser degree. When a koi or goldfish gets to the point when he needs to be euthanized it most often is up to the pet’s owner to do so. We receive many calls throughout the year asking the least painful way they can put their fish to sleep. Although we don’t know for sure what a fish feels we do know what we feel and most of us want to use the least painless route.
There are several humane ways of putting a fish to sleep. Veterinarians often overdose fish with a host of drugs, some people asphyxiate fish using carbon dioxide and others use oil of cloves or grain alcohol.
The Freezing Method
We most often use the freezing method. Koi and goldfish bodies are controlled by water temperature. They go semi-dormant, into a sort of sleep during winter when water temperatures drop. If the water freezes solid the fish will die. Not all fish go into this dormant period and it wouldn’t be right to euthanize a tropical fish this way.
Put the fish in a ziplock freezer bag or large fish bag and make sure he is completely covered in the same pond water from which he came. Place him into the freezer and leave him there for no less than two hours after the water freezes solid. If you bury him remember that wild animals and even some domestic pets can smell him and may dig him up so it’s important that he is buried deeply.
Overdosing With Medication
Most folks do not have these medications hanging around but, just in case, here are some guidelines for using them. Always wait 10 minutes or more before disposing of the fish’s body.
In a container filled with enough pond water to cover the fish add:
Benzocaine over 500 mg
Quinaldine sulfate over 100 mg for 1 min or more
Tricaine aka Finquel over 250 mg for 1 min or more
*Note: Finquel or Tricaine methanesulfonate are the only drugs approved by the FDA for use in euthanizing fish.
Pentobarbital or Ketamine
Oil of Cloves
Oil of cloves is readily available at most health food stores and is often used as a way to anesthetize koi and goldfish. In a container filled with enough pond water to cover the fish add 1 teaspoon per gallon. If the fish is left in too long it will put the fish into an eternal sleep.
Alcohol
Use grain alcohols. Vodka or tequila are good choices. Submerse the fish in straight alcohol the same temperature as his pond water and he will start feeling the effects immediately. I would highly recommend discarding the alcohol afterward — not drinking it. ;)
Asphyxiation (Carbon Dioxide)
This methods sounds awful and it just seems to be less humane to me although it is recommended by many people. For small fish place a couple of Alka Seltzers into the water in a bowl large enough to cover the fish. For larger fish, CO2 (carbon dioxide) can be bubbled into the water until the fish dies.
