Most Humane Way To Kill A Fish: Euthanize Guide | Aquascape Addiction

Most Humane Way To Kill A Fish: Euthanize Guide

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Our Euthanize Guide covers the 3 most humane way to kill a fish and what methods should not be used, along with some useful information.

Most Humane Way To Kill A Fish: Euthanize Guide

There is no easy way to put it, sometimes fish get sick or they get injured and there just isn’t a single thing you can do to make them better. Of course nobody wants to see their fish die, but even worse is watching your beloved pet suffer as they slowly slip away into the afterlife. Now, nobody wants to put their pets down, and that includes fish, but sometimes there is just no other choice so lets look at the most human way to kill a fish.

The bottom line is that killing your fish in a quick and humane way is the better solution to letting the fish die slowly in pain. It’s an uncomfortable and very sad thing to be discussing, but sometimes there is just nothing else left to be done. Here are some of the most humane ways that you can send your beloved pet fish into the afterlife with as little pain and discomfort as possible.

Neon Tetra disease is a common cause for looking into fish euthanizing, here is more information on diagnosis and prevention of Neon Tetra Disease.

An Anesthetic Overdose

Anesthetics are probably some of the best things to use if you want to humanely put down your fish with as little pain as possible. Anesthetics are generally used as pain killers or to anesthetize a fish or animal for surgeries. However, large doses of anesthetics will not only put your fish to sleep, it will also kill them.

Best Way To Kill A Fish Humanely

Here are some of the most common anesthetics that you can use to enthuanize your fish.


The scientific name for this anesthetic is Tricaine Methanesulfonate. This is a commonly used anesthetic by veterinarians and is probably one of the most widely used euthanizing agents for fish. This drug is also known as MS222 and the commercial name for it is Finquel.

This stuff can be found in various drug stores as well as pet stores. In order to kill your fish instead of anesthetizing it, simply give it twice the necessary dose. This stuff is FDA approved for anesthetizing and euthanizing a fish. The fish will simply slip into unconsciousness, stop breathing, and ultimately pass away.


BH stands for Benzocaine Hydrochloride and is often used by veterinarians for euthanizing fish and other pets. This is something that is not available in drug stores and actually requires a veterinarians prescription to acquire. This stuff is more or less like TMS, but a lot more powerful, hence the need for a prescription.

Your best bet is to get a prescription or to simply let your vet take care of it. This stuff is not actually water soluble and needs to be mixed into the fish’s water with either ethanol or acetone to fully dissolve in the water. However, once dissolved it will simply lull your fish to sleep without any pain, and will eventually cause them to overdose in peace.

Clove Oil

Cloves, a naturally occurring plant and food ingredient, contain a chemical that is very toxic to fish. Small amounts of clove oil can actually anesthetize your fish, while larger amounts will euthanize them. All you have to do is to add a significant amount of clove oil to the fish tank or to a bowl with the fish in it. They will lose consciousness and eventually die.

A Barbiturate Injection

Another humane way to euthanize your fish is through the injection of barbiturates, a commonly used sedation and euthanizing type of drug. This is a humane way to kill a fish because injecting barbiturates into the blood stream of your fish will quickly make it lose consciousness, which is then shortly followed by death.

The problem with barbiturates such as sodium phenobarbital, which is one of the most highly recommended euthanizing agents with the least discomfort, is that you won’t be able to get your hands on them. This is only something that can be done by your local vet.

Decapitation Or Snapping Of The Neck

Decapitation is another fairly humane way to end the life of your suffering fish. Some people recommend anesthetizing the fish before decapitation in order to remove any chances of pain and suffering. However the loss of a head is quick and fairly painless. The trick is to not hesitate once you begin and you have to do it fast. The faster you do it the less pain the fish will feel. If you use something like a hatchet or meat cleaver to remove the head with one clean and quick swoop there will be minimal pain.

Moreover, the snapping of your fish’s neck will end their life very quickly as well, much as it does with humans. This is done by putting the fish in a bag and hitting it as hard as you can over the edge of a hard surface, such as the edge of a solid countertop. Keep in mind that you have to be precise and actually hit the neck on the edge, because if you don’t hit the neck bang on it may actually injure the fish instead of quickly killing it.

The result of decapitation or neck snapping is virtually the same, with the aim being to sever the spinal cord in one fowl swoop. In all reality, the better way to go is with decapitation because it ensure that the neck will in fact be broken completely with as little pain and effort as possible.

Methods Which Should NOT Be used

There are some methods of euthanizing fish that have been used in the past, but are usually not accepted as being completely humane. While these methods do the trick just fine, they do often come with a certain amount of discomfort for the fish.


Many people used to freeze a bag of water until partially frozen, then put the fish in the partially frozen water, and then continue freezing it. This is a method that was often used for euthanizing warm water fish. Freezing is a slow and somewhat painful way to go, so it’s really only accepted as being humane when the fish are already anesthetized.

Carbon Dioxide

Another method of fish euthanizing which is no longer accepted is death by carbon dioxide. Fish need to breathe oxygen, so putting too much Co2 in the water will cause them to suffocate. People used to put Alka Selzter in the water because it creates carbon dioxide. This method is no longer viewed as humane. Put it this way, suffocation is a very painful way to die no matter what animal you are.

It is sometimes possible (depending on the circumstances/time) to get a fish breathing again using CPR methods, we have covered a guide here.


This is a very sad topic so we don’t want to dwell on it any more than we have to. The sad fact is that fish get sick and may need to be euthanized. Whatever choice you make and whatever method of euthanization you choose, just try to make sure that you do it right and do it fast because you definitely do not want your fish to suffer any more than they already have.