Humane Ways to Euthanize a Fish

If your fish has become very sick or badly injured to the point where its passing seems inevitable, you may be wondering whether there is anything you can do to ease your pet’s suffering. 

Euthanasia should only be considered in situations where recovery and survival are off the table, and your fish is experiencing pain or poor quality of life as a result of its condition.

In such circumstances, euthanasia may still feel like an upsetting choice, but as long as you carry out the procedure humanely, it’s the kindest option for your fish.

We will be covering the when, why, and how of humane fish euthanasia in this article, as well as pointing out some methods you definitely shouldn’t try. 

Why and When Should You Euthanize a Fish?

The idea of euthanizing a fish can be confusing or downright startling, even for long-term fish owners. 

This is largely because many of us have been conditioned to believe that fish do not feel pain, and therefore, the concept of fish euthanasia can sound quite redundant. 

However, scientific research has shown that fish do, in fact, have nervous systems (although they are different from those of human beings) and can feel pain, although it’s not yet clear how exactly this pain manifests itself.

The sensation is likely quite different from what we experience as humans, but it is an experience of pain, nonetheless. 

What we do know is that fish produce opioids (pain-killing agents), the release of which is triggered by nociceptor neurons (pain detectors). In the past, scientists have tested pain responses in fish through experiments involving acid injections. 

The results, which saw the fish either become devoid of normal defense behaviors (incapacitated) or rub the affected area(s) against surfaces, indicate that fish do feel and respond to pain. 

So, what does this mean in terms of euthanizing a fish? 

Well, simply put, it means that there can come a point where, if your fish is dying, the kindest thing to do is to allow it to pass away peacefully.

It also means that you have a responsibility as an owner to euthanize your fish in the most painless way possible so that you are not inflicting any more suffering on your pet in the process. 

How to Prepare to Euthanize a Fish

Once you have decided to euthanize your fish, the first thing you’ll want to do is remove it from the tank and into a separate container of water. 

This is especially important if the afflicted fish shares a tank with other aquatic animals. Moving the fish to a different container will prevent any potential diseases from spreading. 

Moreover, the most humane euthanasia method for fish, as we will see in a moment, involves the addition of a substance to the water, so you don’t want to have any healthy fish in the same tank or container. 

The other reason it’s important to transfer your sick or injured fish into a different container is that it will make it easier for you to examine the fish. 

Before you euthanize your fish, it’s a good idea to try and determine the cause of illness or injury.

This will allow you to make doubly sure that the condition or injury is irreversible, and if you have any other fish, the results of your examination will let you know what signs or symptoms to look out for. 

When you have your fish in a separate container, look closely at its body for any signs of physical trauma. This could include cuts, scars, or unusual growths. 

If you can’t find any physical signs, you’ll need to check your tank’s environment for potential causes. The water temperature and water quality are common culprits.

If it turns out that your tank is responsible for making your fish unwell, make sure to temporarily remove any other healthy-looking fish from the tank immediately until you can improve the environment. 

After the transfer and examination, your next priority before you carry out the procedure should be making sure that your fish is as comfortable as possible. 

Make sure that the fish still has enough space in its new container to move around as needed and try to avoid making any sudden noises or movements near the container. This will only stress your fish more and aggravate the trauma it is experiencing. 

How to Humanely Euthanize a Fish

If you ask the internet how to euthanize a fish, you’ll probably receive multiple answers. Unfortunately, most of the options you will be provided with, while undoubtedly well-intentioned, are not humane. 

In fact, there are only two methods of fish euthanasia that we would recommend you carry out yourself. 

Clove Oil (Sedation)

To euthanize your fish in the most painless, peaceful way possible, you should use a substance called clove oil. 

Clove oil is a type of essential oil produced by extracting oils from the clove plant. At high doses, clove oil acts as a sedative. Introducing a solution of diluted clove oil to your fish’s water will slowly sedate the fish until, eventually, it passes out and stops breathing. 

This is widely considered by experts to be the most humane way of euthanizing a fish because it is a gentle method. While we cannot conclusively say whether or not the fish experiences any pain during the process, the sedative nature of clove oil makes it very unlikely. 

Compared with some of the other inhumane options we’ll be advising against, later on, it’s definitely the best choice. 

To carry out fish euthanasia by clove oil, you will need: 

  • A container for your fish 
  • A smaller container for the solution 
  • A bottle of clove oil 

When you have safely transferred your fish into its new container, you can set about preparing the clove oil solution in the separate, smaller container. We recommend using something like a mini Tupperware tub. 

The reason you will need an extra container is that adding the clove oil to the fish’s water probably won’t have the desired effect. You will need the clove oil to mix throughout the water, and if you simply add drops to a larger quantity of water, this is unlikely to happen. 

Add some drops of clove oil to a small container of water and stir thoroughly before transferring the solution into your fish’s water. 

Your fish should soon stop moving, meaning that it has fallen asleep. At this point, you will need to add some more drops of clove oil to the water.

This is what will essentially euthanize your fish. About 12 drops should be enough, but if your fish is on the larger side, you’ll need to keep watching for any movement and add more drops accordingly. 

The whole process usually does not take longer than 30 minutes, but if your fish is still moving or showing signs of life after half an hour, you simply need to add a few more drops and wait. 

Baking Soda (Intoxication)

While clove oil is definitely the best method of euthanasia for fish, we understand that it might be difficult to get your hands on some clove oi, especially at short notice. If you can’t get clove oil in time, the next best option is baking soda. 

Dilute about a tablespoon of baking soda in water (approximately one cup) and introduce your fish to the mixture. Your fish will lose consciousness and pass away from carbon dioxide intoxication. 

Note that this method is different from simply introducing carbon dioxide to the tank (see below) because the intoxication causes a loss of consciousness so that the fish does not endure a long and painful death from suffocation. 

Although this method is potentially less humane than clove oil, it’s better than any of the other options and is the next best alternative if you don’t have access to clove oil.

Inhumane Methods of Fish Euthanasia (Do Not Try These) 

Before we move on to the potential for professional (veterinary) fish euthanasia, let’s take a look at some inhumane methods and discuss why you should never use them. 

Blunt Force or Decapitation

Please do not attempt to use blunt force trauma or a blade to euthanize your fish. 

Some people believe that swiftly crushing a fish or decapitating it is the kindest thing to do because it can be done very quickly.

However, there are several reasons why we don’t recommend this option, the first being that in order to crush or decapitate a fish, you will need to take it out of the water. This will cause the fish to struggle and panic because it cannot breathe, which is not a humane thing to do. 

Secondly, while some people see decapitation or blunt force as the quickest option for euthanasia, it’s easy to get it wrong. If you don’t kill your fish with the first blow, you will have caused a very horrible and prolonged death for your pet. 

Plus, even if you do kill the fish quickly with this method, the split second of intense pain is still unnecessary when you have the option of gentle euthanasia via clove oil or baking soda. 

Thirdly, using a blunt object or a knife to euthanize your fish can be very messy, so it’s certainly not a pleasant experience for anyone involved. 

Carbon Dioxide (Suffocation)

We also do not recommend introducing carbon dioxide into your fish’s environment as a method of euthanasia. 

This is the equivalent of suffocating your fish to death. It is traumatic and cruel, and there’s essentially no difference between this method and simply leaving your fish out of the water to die. 

Flushing (Disposal)

Flushing is, unfortunately, one of the most common methods of fish ‘euthanasia’ (it is really just disposal). 

Many people assume that flushing a fish down the toilet will kill it, but this isn’t a guarantee. In all likelihood, your fish will be subjected to a traumatic experience before being exposed to sewage and, eventually, dying. 

We cannot stress enough how important it is not to rely on this method to euthanize your fish as it is inhumane and irresponsible. 

Vodka (Poisoning)

You may see this strategy for fish euthanasia touted as a humane method by some sources, but we strongly advise against it. 

Euthanizing a fish using vodka involves diluting vodka in water at a ratio of 1:4 and placing your fish into the solution. This gives the fish alcohol poisoning and ultimately kills it. 

While we don’t have concrete evidence of how exactly fish experience pain, you wouldn’t want to inhale diluted vodka straight into your lungs, so it stands to reason that your fish doesn’t, either. 

Professional (Veterinary) Methods of Fish Euthanasia

If you feel unable to euthanize your fish yourself, you can take your fish to a veterinarian to be put to sleep. 

Of course, this option will be costly, but your vet will be able to give your fish an anesthetic injection that will allow it to pass away painlessly. 

Rehoming vs. Euthanasia

If your fish is not sick or injured but simply unwanted for whatever reason, please do not turn to euthanasia. 

Your first port of call should be trying to rehome your fish to someone who is able to care for it. 

Most people understand that you should not put down a dog or cat simply because you don’t want to take care of it anymore, so please don’t do this to your fish. 

The Bottom Line

In summary, the most humane way to euthanize a fish is by introducing diluted clove oil to its environment. This will gently sedate the fish and induce a (most likely) painless death. 

If you can’t find clove oil at short notice, you can use baking soda to intoxicate your fish instead. 

Using blunt force or a blade to euthanize a fish is controversial and difficult to do completely humanely, so we advise against this method. 

Similarly, we cannot condone the use of vodka, carbon dioxide, or flushing to euthanize fish. All of these methods cause a slow, potentially painful death.

If you can’t stomach the idea of euthanizing your fish yourself, you can take it to the vet for anesthetic administration. 

Please rehome your fish instead of euthanizing it if you don’t want to take care of it any longer.