How do you Humanely Kill a Fish

How do you Humanely Kill a Fish?

Some painful situations can lead to a question like “how do you humanely kill a fish”? Most fish fish keepers ask this question when their fish contracts a lethal disease or sustain severe injury. Then at this point, death seems better than such painful suffering.  

Now, how do you humanely kill a fish? You can euthanize (painlessly kill) your fish through several ways such as pithing, decapitation, freezing, and using of clove oil. Note that once the method used is more painful than supposed, then it is no longer humane. An example is the common flushing method which proves to be extremely painful. Therefore, it is even better to leave the fish with the disease or wound than painful killing.

While there are several ways to humanely kill a fish, it is important to know when and how to do it properly. And as a fish owner it is in your hands to decide duly.

Lethal Fish Diseases (Fish TB and Whirling Disease)

These two diseases are notorious for being impossible to treat. The first one, Fish TB, is a bacterial infection that is often not treatable, or only treatable with medications not available to the public, and even then, the survival rate is terrible.

Fish TB, or Tuberculosis, can also be transmitted to humans, which makes it dangerous to be around. If you have multiple tanks, it can easily be transmitted and stay dormant for months, only to crop up in a different tank later on.

This illness is very risky, and most, if not all, fish exposed to it will die. In addition, it comes with the risk of you developing terrible bacterial infections and lesions. Due to this, it is better to euthanize the entire tank, rather than let the fish keep living. Even though you may be very attached to these little finbabies, you must take care of your own health first.

Whirling disease is a parasitic infection that is equally as difficult to combat. Euthanizing the tank is normally the easiest way to get rid of it. While this parasite is incredibly rare, it causes severe deformities and neurological damage, so even if a fish does survive, they will be deformed and may not be able to live on their own.

In addition to these two lethal illnesses, there are many others. It is good to be aware of these possibilities, but the good news is that most are very rare. The only one that is not is DGIV, or Dwarf Gourami Iridovirus, which is incurable, lethal, and impacts over 70% of imported dwarf gourami.

So, why would that affect your betta? Betta is a type of gourami, and if there is any cross-contamination between sick gourami and your betta, it may become ill.

When is it Time to Euthanize?

One of the hardest issues in euthanization is determining when you should put down your pet. Some fish can make miraculous recoveries from various illnesses and poisonings, while others may seem to be improving, then pass overnight.

Most of the time, you will not have a vet to tell you whether or not your fish will recover. This makes deciding on when to euthanize very difficult. You can always turn to online fish forums to help make a decision or diagnosis, but not everyone will be accurate.

Some big warning signs that you fish will pass soon tend will be bottom sitting, rapid or shallow gill movement, glossy eyes, open sores, severely sunken stomachs, and several others.

For example, if your fish is simply old but is having issues swimming and cannot make it to the top of the tank or eat properly, it may be time to consider euthanization.

If your fish has a swim bladder issue that causes it to float, this is not often lethal, but may lead to some part of the fish being forced out of the water. If this is the case, that part will dry, crack, and bleed. It is inhumane to leave your fish in this condition, and they should be euthanized.

Some fish come exposed to internal parasites, which are normally easy to treat. That being said, some will likely be too far gone before you buy them, and you may not even realize it. Once they have severely sunken stomachs that extend past the belly area, they will not recover.

Some Common Methods of Fish Euthanization


Pithing is a method of euthanization that, while gory, is one of the kindest options out there. It involves using a sharp and small object to destroy the brain. Sensitive readers should skip this part and move to the next option; while the next option takes a little longer and may cause pain, those sensitive to gore can use that method.

A fish’s brain is above and behind the eyes, though you should look at anatomical charts of your specific species of fish to make sure you get it right. While most professionals use a sharp and slim object, like a thick needle, a knife is also acceptable.

With a needle, you need to quickly pierce the skin and get to the brain, then swirl the needle around to destroy the brain. The brain has no nerve endings, which means no pain can come from that region. By quickly destroying the brain, the fish will pass instantly and without pain.

A knife can also be used, though it is much more messy and associated with a bit more pain, though the fish may pass before being able to register it.

Clove Oil

Clove oil is a popular method for those who are not willing to use some of the gorier methods. This method is simple, though it may cause some pain to the fish. The first thing you need to do is to remove the afflicted fish to a separate container (with water from the tank).

In a separate container, such as a medicine bottle, mix several drops of clove oil and water, and shake vigorously. Slowly pour the solution into the container with your fish. The fish will likely become more active and start gasping more but will soon become unconscious.

After they are unconscious, you may add more of the clove oil mixture until you no longer see any gill movement. Twenty to thirty minutes after the last gill movement, your fish has passed and can be disposed of.

Instead of extra clove oil, you can also dose vodka, but you must be sure that your fish is entirely unconscious. The vodka will otherwise cause extreme and unnecessary pain.

If you need to get rid of an entire tank with multiple fish, dosing clove oil into the tank as described above is one option, though nothing in the tank can be reused.


Decapitation is similar to pithing in that it is gory, but is also nearly entirely painless for the animal. Severe the spine as close to the base of the brain as possible. Expect some muscle movement after death for both this method and for pithing.


Freezing is another method that can be used by those adverse to gore. Take your fish and place them in a separate container of water, then either move that container into a freezer or an ice bath. Fish are cold blooded, so their metabolism will continuously slow down until they are unconscious, then they won’t wake up.

While this sounds like a pleasant method, it cannot be determined whether or not a fish feels pain during this. Some fish, such as cold water and temperate ones, do not seem to, but bettas are tropical fish, so they may feel some pain from this method.

What NOT to do

One thing that many do to “euthanize” a fish is to flush it. This is one of the most painful ways for a fish to die. The chlorine in the toilets will burn their gills, scales, fins and any other part of them. If the burns don’t kill them, being bashed around all the piping will.

This is a very painful and inhumane way to kill a fish, as is taking your fish out of the water. For betta, it will take several hours for them to die this way, and they will dry, crack, and bleed before dying a terrible death.

And boiling… Do you want to die by boiling? No, the answer should be no. That’s what your fish thinks anyway.

As mentioned, you can use clove oil to make a fish fall unconscious then use vodka to euthanize it. However, if you attempt to use vodka alone, this will result in a massive amount of pain for your fish and could never be considered humane.

In conclusion

There are times where the best method of care for your fish is euthanization. The reasoning ranges from an illness to a severe injury, but the end result will be the same. The best method of euthanization is either pithing or decapitation, though clove oil is a good alternative for those adverse to gore.

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