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3 Methods To Humanely Euthanize Your Pet Fish (And What NOT To Do)

As fish keepers, we strive to provide a comfortable and engaging environment for our beloved pets to flourish and thrive. However, when a fish is aged or suffering greatly from disease or poor care, euthanization may be the only humane option. It’s important to understand how to humanely end a fish’s life.

Euthanasia, the humane killing of an animal, is never easy. It’s the hardest part of caring for pet fish. Before discussing humane methods, it’s important to determine when euthanasia is the appropriate decision.

When Should You Euthanize Your Pet Fish?

Generally speaking, it’s up to each owner when they feel it’s time to euthanize. The standard for when to euthanize is essentially whenever you feel that the animal is suffering beyond what it should. If your fish is perfectly healthy, there is no real reason to euthanize it.

Some may euthanize the fish when they’ve exhausted all other options for the treatment of a disease. It’s also perfectly acceptable to euthanize if one feels the treatment of a disease may cause too much additional suffering. For instance, old age or Dropsy may require euthanasia, while conditions such as Columnaris or Swim Bladder Disease (SBD) may not.

Accidents can happen in the tank, such as injury from an aggressive tank mate, a spike in toxic chemicals due to a forgotten or failed aquarium cycle, or harm from adding chlorinated tap water. Parasites, such as Planaria and Hydra, can cause mechanical, psychological, and reproductive damage (1). They often enter the tank through new fish or plants or through gravel from another tank.

Use a humane method for euthanasia as there is growing consensus among scientists that fish don’t feel pain (2). However, many in the fishkeeping hobby believe that fish can experience a range of emotions, including joy, curiosity, stress, and suffering.

Let’s examine the humane methods used by fishkeepers and veterinarians.

Three Ways to Humanely Euthanize Your Pet Fish

There are only three humane ways to euthanize a fish. Methods such as freezing or alcohol baths are considered inhumane and can cause unnecessary suffering for your fish.

Method One: Euthanasia with MS-222 Anesthetic

MS-222, also known as Tricaine Methanesulfonate, Finquel, or Tricaine-S, is an FDA-approved drug for fish anesthesia (3). To use this method, add 5-10 times the amount recommended on the label, usually 250-500 mg/L, to the fish’s water. This will slowly put the fish to sleep and stop its heart by lowering the level of oxygen in the body. This method is commonly used for larger fish such as Clown Loach, Oscar, and Angelfish.


  • Good for larger fish
  • Quick and easy
  • MS-222 is FDA approved fish anesthetic


  • Can be expensive

For smaller fish like Betta and Danios, another method for humane euthanasia is available.

Method Two: Clove Oil Bath Euthanasia

Clove oil and its major compound, eugenol, have sedative or anesthetic properties. It can be easily obtained from supermarkets, health food shops, and chemists.

Studies on Zebrafish have shown that using clove oil for euthanasia is less stressful for the fish than other methods (4). The American Veterinary Medical Association (AVMA) also recommends clove oil as a humane method for euthanasia.

Clove Oil for Euthanasia
Clove oil for euthanasia

Here’s how to euthanize your fish with clove oil:

Step 1: Prepare a Small Container for Your Fish

Place your fish in a small bucket or bowl filled with tank water (or dechlorinated water). Avoid using tap water as it contains chlorine that can harm your fish. Ensure that the water level is a little more to cover the fish’s body.

Step 2: Mix the Clove Oil Solution

You can’t add clove oil directly to the bowl. Because it’s an oil, it won’t mix easily with water. So, mix up a solution separately.

To prepare the clove oil solution, use a container with a lid or a bottle with a cap. Add 400mg of clove oil to every quarter-gallon of tank water and shake it well to mix. Ensure that the solution is thoroughly mixed, with no beads forming.

Step 3: Add the Solution to the Fish Container

Add the clove oil solution gradually to the fish bowl. Adding it all at once can shock the fish and cause distress. Instead, add a few drops at a time and stir the solution into the water.

This process may take five to ten minutes. Your fish will become relaxed and lose consciousness.

Fish losing consciousness
Fish losing consciousness

Step 4: Completing the Euthanasia

After 30 minutes, check for any gill movement and eye-roll (movement in the eyes when the fish is picked up and rotated) to ensure the fish is no longer alive.

If the fish shows no signs of life, bury it in a flower pot or outside by plants or trees to continue the cycle of life.

For larger fish (more than 4 inches in length), add an additional 12 drops of clove oil per quarter-gallon or liter. This should be enough to stop the fish’s breathing and cause it to die while sleeping.

  • Won’t stress the fish if done properly
  • Easier to perform for pet owners
  • May require pithing if not done properly, which can make this method inhumane.

Method Three: Blunt Force Trauma Euthanasia

Blunt Force method involves delivering a quick, painless death by striking the fish with a blunt object. It may not seem humane at first glance, but it’s approved by the American Veterinary Medical Association (AVMA).

However, it’s not recommended for those who are easily disturbed. If you are uncertain about this method, consider using clove oil instead.

Step 1: Hold Your Fish Securely

To begin, obtain your fish and place it on a square of aluminum foil. Carefully wrap the foil around the fish, making note of its head’s location.

Step 2: Apply the Blunt Force

Using a tool such as a brick, rolling pin, or another blunt object, hit your fish’s head through the aluminum foil. You can’t be a wimp: hit your fish as hard as you can, it will create a potential mess of blood and bodily fluid. It’s more humane to finish the job in one blow.

This will kill your fish outright and certainly disable the nervous system. But to be sure he isn’t stunned, there’s another step to perform.

Step 3: Pithing (Stabbing Your Fish)

The force of the previous step either killed your fish or left him unconscious, so you can perform this step humanely. He won’t feel any pain.

Unwrap your fish from the foil and using a sharp knife, cut it into his brain. This is called pithing. You’ll find your fish’s brain behind his eyes, so carefully cut between them and back into his skull.

This will kill your fish instantly. While it may seem violent and barbaric, it’s painless and completely humane.

  • Can be performed using common household items
  • Can be stressful for the fish
  • Easy to make mistakes

How to Not Kill Your Fish

It’s important to note that there are many cruel ways to end a fish’s life, some of which may be considered by fish hobbyists.

1. Never Flush Your Fish

Flushing a fish down the toilet is inhumane and not an effective method of euthanasia (5). Unfortunately, it’s a common method used by people who have impulsively bought a pet fish or won a Goldfish at a fair.

While the changes in water temperature, chlorine, or toxins in human feces may kill the fish quickly, it may also survive the experience. Regardless, the fish will experience pain in an environment it was not meant to live in.

Additionally, flushing a fish is bad for the local ecosystem. It risks introducing illness and bacteria, viruses, and parasites into drinking water systems and natural waterways, which can be harmful to native plants and animals.

2. Avoid Freezing Your Fish

Placing a fish in the freezer or refrigerator is a slow and inhumane way to cause death.

As the fish freezes, ice crystals form in its gills, causing immense pain and difficulty in breathing. This is a form of torture that can take hours for the fish to die, and it will be in pain throughout the process.

3. Ice Baths are Not Safe

Ice baths at a temperature below 39 degrees Fahrenheit can be a humane way to kill smaller tropical freshwater fish, as indicated by scientific studies on Zebrafish. However, the effectiveness of this method varies depending on the age of the fish.

It’s important to note that if ice crystals form on the fish’s gills, it may experience pain.

It’s also worth noting that some fish, such as Goldfish and Koi, can survive in cold water. An ice bath may not be an effective or quick method for killing these types of fish.

4. Alcohol Baths are Dangerous

It’s not safe to place your fish in an alcohol bath, such as vodka. Alcohol is toxic and will cause severe damage to the fish’s gills, leading to death. An alcohol bath is inhumane and should never be done to a fish.

5. Carbon Dioxide Suffocation in Water

Fish absorb oxygen from the water through their gills. Injecting carbon dioxide into the water reduces the oxygen content and can lead to suffocation and death. This process is stressful for the fish, as they must constantly struggle for oxygen. It’s a slow and inhumane way for a fish to die.

6. Leaving Your Fish Outside The Tank

Leaving a fish outside of its tank can be fatal as it can no longer absorb oxygen from the water through its gills. Even tropical fish with labyrinth organs are unable to get enough oxygen from the air when not in water.

This can lead to a slow and painful death as the fish suffocates and its organs fail. It’s important to always keep your fish in its appropriate tank or aquarium.

7. Never Boil Your Fish

Boiling water is an effective method for cooking lobsters, but it’s not recommended for fish.

When the water temperature consistently rises, dissolved gases such as oxygen will escape at a faster rate. This can make it difficult for fish to survive and can lead to suffocation, ultimately resulting in the death of the fish.


Euthanasia is a last resort for fish that can’t recover. It’s considered the most humane option.

However, if there is no need to euthanize your fish, it shouldn’t be done. Instead, consider rehoming your fish with friends, and family or reaching out to local pet stores. There is usually someone interested in caring for an unwanted fish. You can also find fishkeeping hobbyists on social media platforms such as Facebook or Reddit who may be willing to adopt a fish.

Saying goodbye to a pet can be difficult, but it can be made a little easier when you know it’s the right decision. If euthanasia is the only option, it should be done in a humane manner.

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