How to Euthanize Fish: The Most Humane Ways of Putting a Fish to Sleep

As a pet owner, I know that it is hard enough knowing and dealing with a sick pet especially if you are caring for fishes. However, knowing when to make a decision to end your pet?s suffering is harder and will often make you think on how to euthanize fish in the most humane way possible.

Clearly, this is a decision that is not to be taken lightly and an action that should be all the more executed with caution. Euthanasia in fish or other pets has been an option many would consider especially if your pet is suffering from a terminal disease and can no longer have a good quality of life.

This guide will provide you with the different approaches on how to euthanize fish. Furthermore, it will also give you several tips that can also be an additional use for you.

What You Will Need

A few important things will be needed to properly execute this process. Here are the following particulars that you need for this task.

  • Tricaine Methanesulfonate (MS222 or Finquel) - an anesthetic that can be used to humanely euthanize fish.
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    Benzocaine Hydrochloride - an anesthetic that requires a vet?s prescription and can also be used to euthanize fish.
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    Barbiturates - a substance that is also often used for anesthetizing and euthanizing fish. This substance is injected directly into the bloodstream.

How to Euthanize Fish?

There are three known and accepted methods of how to euthanize fish and another two approaches that are conditionally acceptable.

Be that as it may, before you make the ultimate decision to euthanize you fish, I would also recommend that you seek a professional's advice for a more in-depth understanding of the whole process.

When all the materials have been gathered for this process, you can now proceed with going through the guide as follows. Here are the different approaches on how to euthanize fish.

Acceptable Methods of Euthanasia in Fish

  • Overdose with Anesthetics

1. Tricaine Methanesulfonate or also referred to as MS222 and known as Finquel commercially is a substance used to anesthetize a fish. This is approved by the FDA for both anesthetizing as well as euthanizing fish.

It is noted as the most humane way to euthanize a fish according to many pet owners and veterinary doctors. Administering double the recommended amount for anesthetizing will euthanize your fish.

To understand how this substance works, watch this video:

2. Benzocaine Hydrochloride is another anesthetic you can use to euthanize fish. However, this substance cannot be purchased over-the-counter and requires a prescription from a veterinarian. 

They highly recommend not using Benzocaine alone because it is not soluble in water, while Benzocaine Hydrochloride can be immersed in water.

3. Barbiturates, on the other hand, is a substance that needs to be injected into the bloodstream for the process of euthanizing fish.

This substance renders the fish unconscious which is followed by its eventual death. Barbiturates also require a veterinarian?s prescription for you to obtain it.

  • Conditionally Acceptable Methods of Euthanasia in Fish
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Blow to the Head:

This method may not sound gentle but is one of the two methods that are conditionally acceptable for euthanizing fish. A hard blow directly to the head of the fish will lead to its death. For this method, you can use any hard object to strike the head of the fish with.


Another method that is conditionally accepted by professionals is decapitation. This is a swift move for euthanizing fish. For this, you will require a very sharp knife. The method is done by holding the fish down and in one swift and powerful move, cutting off its head.

Additional Important Tips for Euthanizing Fish

1. One of the most important things to do before taking any action is to ask the advice of a trained professional, in this case, a veterinarian to assess the situation of the fish and recommend which method is best to execute.

2. If you are opting for a method of euthanasia that involves any drug substances, it is more efficient to withhold food about 24 to 48 hours before administering the drug. This will allow faster absorption of the drug since the fish is on an empty stomach.

However, do not do this if no drug is involved with the approach you have chosen.

3. If you are dissolving the drug into the water, use another tank for this process. This is best especially if not all the fishes in your tank need to be euthanized. Transfer some of the water from the old tank to the new one for it to have the same water condition.

The difference in water condition can cause stress to the fish resulting in an inhumane death.

4. If in case you preferred the physical method of euthanizing fish like a blow to the head, you need to make sure that the fish is indeed dead. Some fish can remain conscious even after a hard blow to the head. In case, you can carry out the process by decapitating its head off.


In conclusion, it is a big decision to make if you are considering euthanizing your fish. As a pet owner, it has to be in the most painless, swift, and humane way as possible.

Before taking any action, it is best you seek the advice of a veterinary doctor for you to make sense of the whole process. These methods, that I have discussed were approved by professionals, however, understanding them with perfect clarity will also do you good.

Do you find the different approaches on how to euthanize fish easy to follow? Were the additional tips helpful? Do you have any other suggestions about this topic?

I would like to know your views regarding this article. Send your reactions and suggestions by leaving a comment below. 

John Morris

Hi, I?m John Morris. I?m an avid outdoorsman and fisherman, blessed with an awesome wife and 2 kids. Fishing is not my passion, it is my lifestyle. I fished before I knew how to walk! I?m obsessed with all things related to fishing, even the fishy smell. I?m always willing to extend a hand to novice anglers looking for fishing tips and tricks thus I created this blog. This blog is a collection of my experiences, knowledge, and also research from other blogs.

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