How Can I Humanely Euthanize My Pet Fish? All the Options


If you are contemplating euthanizing your pet fish, there are a few things to keep in mind. First, be humane. Don’t try to kill the fish with a blunt object or with hot water. Choose a method that will be painless for the fish.

Aquarium fish vary greatly in size and physical adaptation to their environments (salt water, fresh water, etc.). Therefore, there is no single solution for how to humanely euthanize all fish. Commonly recognized methods suggest anesthetic overdose, clove oil, and physical decapitation.

Continue reading to learn more about euthanasia and each of these methods.

What Is Animal Euthanasia?

Animal euthanasia is the act of killing an animal or allowing it to die for the purpose of minimizing physical suffering and distress. Generally, it is used when an animal becomes excessively injured or when it has an incurable condition or disease that is likely to cause it pain.

Is Animal Euthanasia Humane?

Animal euthanasia is a method that serves to end the pain and suffering of animals; yet, sometimes animals are also euthanized at the owner’s request, a.k.a. convenience euthanasia. In general, it would seem that animal euthanasia is a humane act. However, Frontiers in Veterinary science states that many veterinarians lack the tools for animal quality of life assessment and ethical decision-making when it comes to deciding whether or not to take an animal’s life.

When Is It Ok to Euthanize a Fish?

Heather Candelaria from the Greater Seattle Aquarium Society suggests three reasons for when it is appropriate to euthanize a fish.

  1. When stress can kill. When a fish is unable to perform its basic biological functions such as finding and consuming food, escaping predators, and engaging in procreative activities. Fish that are under a large amount of stress are likely to eventually die on their own.
  2. When disease occurs. Disease in fish is highly contagious and is very difficult to treat. If one fish is sick it is likely to spread the disease to your other fish.
  3. When breeding fish. Oftentimes when breeding fish, especially for selective characteristics, some fish are selectively “culled” due to their poor characteristics that may lead to mutations in future generations.
Betta in small container
It is best to separate the fish you need to euthanize from the rest

How Can I Tell if My Fish Is Sick?

According to The Veterinary Nurse, there are a number of ways that you can tell if your fish is sick. Be sure to pay attention to the following behavioral changes such as:

  • loss of appetite;
  • weakness or lack of interest in swimming;
  • lack of balance or buoyancy control;
  • erratic swimming;
  • clamped fins (flat against the body);
  • gasping or mouthing for air;
  • increased respiration rate;
  • becoming unusually antisocial; or
  • staying at the surface of the water.

How Can I Tell if My Fish Has a Disease?

The Veterinary Nurse also states that it is important to be able to recognize whether your fish is ill due to tank conditions (temperature, oxygen, etc.) or disease. If your fish has a disease, you may notice some of the following changes in addition to those mentioned above:

  • color change;
  • cloudy skin;
  • bumps or swelling;
  • change in body shape such as a sunken belly (a large head and small body);
  • change in gill appearance; or
  • carrying long fecal trails that are longer than a quarter size of the fish.

What Is an Anesthetic Overdose?

Anesthetic overdose is when a large amount of anesthetic, a substance that minimizes sensitivity to pain, is dissolved in water. The RSPCA suggests that this method is safe and humane and especially appropriate for large fish that are difficult to handle. This procedure must be carried out by a veterinarian because the recommended anesthetic is not available to the general public.

What Is Clove Oil?

Clove oil is an essential oil that is derived from clove trees. One of the most well-known benefits of clove oil is its ability to act as a sedative. These sedative properties can be used to euthanize small aquarium fish. t can help to calm and relax the fish reducing the chance of stress or anxiety in the fish.

Clove oil is readily available for consumers.

Now Foods Essential Oil, Clove, 4 Ounce (1 Glass Dropper Included)

How Do I Use Clove Oil to Euthanize My Fish?

The RSPCA states that adding approximately 0.4 mL of clove oil per 1.0 L of water into the aquarium should be enough to cause fish death. The RSPCA suggests mixing the clove oil with warm water and adding it to the aquarium water slowly over a period of five minutes to avoid unnecessary stress on the fish.

What Happens to Fish Exposed to Clove Oil?

When fish are exposed to clove oil at the above concentrations, they will lose consciousness, stop breathing and then die due to hypoxia. Hypoxia is the state of having low levels of oxygen in your blood and tissues.

The RSPCA warns that the concentration of the clove solution must be appropriate for the fish size and that the fish must remain in the water for 10 minutes after all signs of gill movement have stopped. They also suggest placing the fish in the freezer to ensure that they die and so that you are able to dispose of them safely.

What Is Physical Decapitation?

Companion Animals describes decapitation euthanasia as the removal of the fish’s head from its body followed by the destruction of the brain (pithing). They note that, unlike mammals, fish can remain conscious after decapitation due to their physiology, therefore pithing is essential for destroying the central nervous system.

Physical euthanasia should only be performed by competent fish handlers because this method can cause a lot of stress on the fish if done poorly. Generally, most people feel uncomfortable with this method so it is best to only perform it with some training to avoid hesitation.

How Do I Verify the Fish Is Dead?

RSPCA states that you can consider the fish to be dead when thirty minutes have passed since the last gill movement or loss of eye-roll while the fish is moved side to side.

What Are Inhumane Methods of Euthanasia?

The aim of humane euthanasia is to kill the animal in the shortest time possible while causing it the least amount of stress. While there are many different ways euthanasia can be considered inhumane, the RSPCA notes that the most common methods are:

  • flushing it down the toilet;
  • immersing it in ice water or putting it into the freezer;
  • boiling it in hot water;
  • suffocating it by leaving it out of water; or
  • decapitation without stunning or pithing.

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