How To Humanely Euthanize Your Fish

It’s never an easy decision, but it’s our duty as pet owners to act in our fish’s best interest.

If you’ve got a sick fish and want to gently put it out of misery so it can rest peacefully, read this guide to learn how to euthanize your fish in a humane manner.

Methods I Don’t Condone

Let’s just get this out of the way.

There are some methods that pop up on the internet that are just ridiculous, and frankly, downright cruel in my opinion.

Please, don’t use these methods: 

  • Throwing fish on the ground to stun them.
  • Flushing them down the toilet while they’re still alive.
  • Leaving them out of water until they suffocate- this is slow and very uncomfortable.
  • Bashing fish in the head with a hammer – you could miss and cause a great deal of pain.
  • Putting fish in the freezer – this is slow and can be painful for fish.
  • Putting fish into boiling water – terribly painful way to die.

I can’t believe that anyone would even think that last one was an option, but I did come across it online

Some people do recommend decapitating fish. This would kill them very quickly, but if you get it wrong, this could lead to a lot of suffering for the fish.

So unless you’ve got some experience with decapitating fish, and know you can quickly cut off the fish’s head completely, I don’t recommend this method either.

How to Humanely Euthanize Fish

Overdosing fish on prescription level anesthetics is the best way to make sure that they don’t suffer.

But, these drugs aren’t available to the public and many of us don’t have a local veterinarian that treats fish.

So let’s go over how to euthanize fish with things that are readily available to the public. This is a fairly controversial topic that’s endlessly debated online in aquarium forums. 

I’m presenting you with what are, in my opinion, some of the best ways to euthanize fish at home so that they don’t suffer needlessly.

From here, it’s up to you to decide which method you are most comfortable with.

Clove Oil

Pros: 

  • Painlessly puts fish to sleep and then kills them.

Cons: 

  • Takes a long time.
  • Risk of not fish not dying and waking up later.

Clove oil is an essential oil derived from the buds, leaves and stems of the Syzygium aromaticum plant. The active ingredient is a compound called eugenol that has numbing properties.

You can buy clove oil from specialty health food stores, herb shops or even on Amazon.

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    Clove oil is used to anesthetize fish so that minor surgery can be performed while they’re asleep.

    But, if you leave the fish long enough, the eugenol will kill them.

    This is a great way to painlessly euthanize a fish, but you have to make absolutely sure that you leave the fish exposed to the clove oil long enough.

    Otherwise, the fish might seem dead but really it’s just deeply, deeply asleep and capable of waking back up.

    Equipment

    • Container to put your fish in, appropriate to size
    • Clove oil
    • 2 ounce jar or container with water tight lid
    • Warm water
    • Medicine dropper
    • Air pump
    • Airstone
    • Airline tubing

    Steps

    1. Figure out exactly how much water the container you plan to use for the fish holds. You’ll need to know this so you can dose the clove oil properly.
    2. Fill the container with enough tank water so that the fish can rest comfortably.
    3. Set up the airstone, airline and pump so that there are continuous bubbles in the water. This will keep the clove oil dispersed in the water column. 
    4. Half fill the small jar/container with warm water.
    5. Use a medicine dropper to drip clove oil into the jar. You’ll need 0.5 ml (about 10 drops) per liter of water in the big container. That’s roughly 2 ml (½ teaspoon) per gallon.
    6. Put the lid on your jar and shake it vigorously until the liquid becomes milky looking.
    7. Net the fish and place it into the container.
    8. Slowly pour the clove oil mixture into the container with the fish.
    9. The fish will calm down, then gently go to sleep, turning belly up.
    10. Leave the fish in the container for at least an hour to make absolutely sure that it has died.

    Alka Seltzer 

    Pros: 

    • Very quick method of killing fish
    • Alka Seltzer is readily available

    Cons: 

    • Fish briefly thrashes

    Adding Alka Seltzer will also quickly euthanize a fish. When you drop the tablets into the water, there is an instant chemical reaction between the citric acid and the sodium bicarbonate (baking soda) that causes carbon dioxide (CO2) bubbles to rapidly form. 

    The CO2 quickly depletes the oxygen in the tank, killing the fish.

    I have used this method several times over the years and can attest that it works very, very quickly, within seconds in my experience. I always leave the fish in the water for at least 10 minutes to make sure that it has died and won’t revive if put back in an oxygenated environment.

    I’ve never had a fish revive, but I’d rather be safe than sorry.

    The one con to this method is that the fish does briefly thrash. Some argue that this is evidence that the fish goes through some level of suffering before it dies.

    Look, I can’t give you absolute scientific proof that the fish does or does not suffer. But I can say that within seconds the fish stops moving altogether and dies.

    So I definitely don’t think there is any prolonged suffering.  I do leave the fish in the Alka Seltzer water for at least 10 minutes to make absolutely sure that they’ve died.

    This is probably overkill, like literally, but it makes me feel better.

    Equipment:

    • Container to put your fish in, appropriate to size
    • Alka Seltzer tablets (8 tablets per gallon/ 2 tablets per liter)

    Steps:

    1. Fill the container with tank water, net fish and place it in the container.
    2. Add 8 tablets per gallon of water.
    3. Tablets will fizz strongly as they dissolve, fish will thrash for a few seconds and will then float to the top of the water.
    4. Leave fish in the container for at least 10 minutes to ensure it has died.

    How to Dispose of Dead Fish

    I know a lot of people think that you should just flush dead fish down the toilet. Well, little ones at least.

    But I don’t recommend this. Flushed fish can end up in local waterways.

    Then they might pass the bacteria, virus or parasites that killed them to native fish. This can have devastating effects on local fish populations.

    Instead, I would recommend placing the fish in a plastic bag and disposing of it in the garbage.

    It’s better to be on the safe side and protect wild fish whenever we can.

    Final Thoughts

    I hope I’ve given you some insight into how to best euthanize your fish so that you can minimize their suffering. 

    The decision to euthanize a fish is never an easy one. But, it’s our duty as pet owners to always act in our fish’s best interest, even if that means ending their life to prevent further pain.

    If you’re reading this article, then you probably have a very sick fish and you’re looking for ways to put it out of its misery. 

    I’m sorry you’re going through that. That’s awful, and I wish you all the best.

    I know that I get very attached to my fish and it can be really difficult for me when one is so sick that I have to euthanize it. 

    Luckily, it’s been rare in my years of fishkeeping, but that doesn’t make it any easier.

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