How to Humanely Kill a Pet Fish: Ethical Euthanasia Options

Published June 30, 2022
Man using aquarium net to catch a fish

There may come a time when your pet fish becomes very ill. If they have a grave prognosis or nothing can be done to treat their condition, often the kindest thing to do is help them pass on. There are numerous possible ways to humanely kill a fish. However, some of the traditional methods, such as freezing or flushing them down the toilet, are considered pet fish abuse. Instead, the use of clove oil is an inexpensive and veterinarian-accepted approach to compassionately end a fish's life.

When Is It Ethical to Kill a Pet Fish?

Euthanasia of any species should never be taken lightly, including that of pet fish. Euthanizing healthy fish simply for convenience is not ethical. However, it may be appropriate to consider humanely killing pet fish in certain scenarios, including in the event they suffer significant injury, have a terminal illness, diseases that have failed to respond to multiple rounds of treatment, or contagious outbreaks with a high risk of affecting and killing other fish in the tank.

If you're unsure whether your fish's condition is treatable, consult with a veterinarian or speak with an aquatic expert wherever you purchase your fish supplies. It's possible there is a solution that could help your fish, but if you've tried everything, it may be time to say goodbye.

How to Humanely Euthanize a Fish

Contrary to popular belief, experts believe that fish do experience pain. Fish possess nociceptor sensory neurons that respond to painful stimuli, such as injuries, heat, or extreme cold. Therefore, carefully consider how you plan to euthanize a pet fish, just like you would with any other companion animal.

The American Veterinary Medical Association (AVMA) outlines guidelines for veterinarians regarding humane euthanasia practices. This information enables vets to choose the most appropriate method to end an animal's suffering without causing unnecessary pain or putting others in danger, among other criteria.

Vet injecting sick fish

In aquarium and veterinary settings, professionals have access to various pharmaceuticals and techniques to assist in euthanizing fish. The same euthanasia solution that is used in companion mammals such as dogs and cats can also be injected into fish. However, due to their aquatic environment, it's most common for veterinarians to use an immersion agent in the fish's water, such as MS-222, which is also known as tricaine. They cannot dispense these substances for you to use at home, however, and you will have to bring your fish to your vet's office for the procedure.

Clove Oil as a Humane Way to Kill Pet Fish

According to the AVMA, clove oil, which contains high levels of the compound eugenol, is an acceptable euthanasia agent for fish. At low doses, this substance can be used as an anesthetic, but with higher concentrations, it will cause a fish to become sedated, stop their respiration, and result in death. Clove oil is easily accessible and inexpensive, so many aquatic hobbyists elect to humanely kill their dying fish using this oil.

Clove oil in bottle and cloves

Studies suggest that the concentration necessary for euthanasia is a minimum of 0.4 milliliters of clove oil for every 1 liter of water. Do not use clove oil in your main tank. Prepare the solution in a separate vessel to avoid contaminating the entire aquarium. The fish should be left in the solution for at least 30 minutes after their respiratory movements stop. Eugenol is carcinogenic, so use care when handling or disposing of the oil for this or any other purpose.

A person or any other animal should not ingest fish that have been euthanized with clove oil, according to the Food and Drug Administration (FDA). Therefore, this method should not be used in fish caught for consumption.

Inhumane Ways to Kill a Fish

Several of the traditional methods of euthanasia are considered unethical and inhumane. These include:

  • Flushing a fish down the toilet.
  • Placing a fish in the freezer.
  • Removing a fish from the water to suffocate.
  • Placing a fish in boiling water.
  • Decapitation without anesthesia or pithing.
  • Stunning a fish without anesthesia or pithing.
  • Blunt force trauma without anesthesia or pithing.

Physical methods of euthanizing fish are acceptable when executed by veterinarians, including blunt force trauma, decapitation, and severing of the spinal cord, all followed by pithing. However, they should never be performed by someone inexperienced or unqualified. Without the right technique, the fish can experience extreme pain. Following these methods, pithing -- which is the process of probing the brain to destroy the brain tissue -- is necessary to give a fish a humane death.

Never Flush a Fish Down the Toilet

Whether your fish is healthy, dying, or dead, it is never acceptable to flush them down the toilet. It's unlikely that a fish will survive the flush, but if they do, they could compete with local fish species. Plumbing is designed for human waste, not animals. Therefore, even a small fish could potentially cause harm to your pipes. Additionally, diseased fish carrying parasites or bacteria can impact the local environment or even spread illness.

Planning the Death of a Pet Fish

Making the choice to end a pet's suffering is never easy. If you've decided to let your fish go, the best course of action is the seek veterinary care. Your veterinarian can recommend the most humane way to kill your pet fish, either in the hospital or in the comfort of your home.

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How to Humanely Kill a Pet Fish: Ethical Euthanasia Options