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What Are the Different Reasons to Euthanize a Fish?

Euthanizing a fish is a compassionate choice when it's suffering with no hope of recovery. Reasons include terminal illness, severe injury, or an untreatable disease that affects quality of life. It's a humane decision to prevent unnecessary pain. Considering this step? Learn more about the signs that indicate it's time and the most humane methods available. What will you decide?
Alex Tree
Alex Tree

The primary reasons to euthanize a fish are injury and disease. A fish can be injured by an aggressive tank mate or a sharp tank decoration that needs removal. A lot of disease can affect aquarium fish, from the common fin rot to dropsy, a disease that causes the fish to bloat. Fish diseases are usually obvious because they significantly alter the fish’s appearance or result in the fish no longer eating or swimming correctly. It is possible to humanely euthanize a fish so that it suffers very little or not at all.

Some aquarium fish are highly aggressive and must be kept alone, or else they will attack their tank mates until none are left alive. Even normally docile fish can attack one another until death of an opponent. It is common for semi-aggressive fish to occasionally injure another fish. These injuries often heal with no intervention needed, though it is usually recommended to separate the injured fish from the aggressors. Not all fish fights have happy endings, though, and it may be necessary to euthanize a fish that has been severely injured and will only suffer until its inevitable death.

Clove oil, which can be used to euthanize a fish.
Clove oil, which can be used to euthanize a fish.

A few viral diseases often affect domestic fish and can usually be spotted fairly easily. For example, fish pox can usually be spotted by the appearance of gray or pink growths on the body of a fish. Furthermore, lymphocystis, which is often brought on by poor living conditions, can often be spotted by the appearance of brown wartlike growths. Another condition, called Hexamita, is caused by parasites and is typified by fish becoming lethargic and lesions appearing on their heads. When a fish experiences this condition, it will usually become visually smaller due to poor health.

Vodka, which can be used to euthanize a fish.
Vodka, which can be used to euthanize a fish.

Clove oil is often regarded as the most humane and simplest way to euthanize a fish. This oil is a substance that can be added to a fish’s aquarium and, if dosed properly, the fish becomes unconscious. It should be kept in mind that utilizing clove oil alone for this purpose is difficult because a large amount of it would be needed. Instead, an alcoholic substance such as vodka can be added to the aquarium after the fish is put to sleep with clove oil. Whatever method is used, it is important to make sure that the fish is actually dead and not simply asleep and to anesthetize and then euthanize the fish in the appropriate order.

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Discussion Comments


What is the best way to clean my tank? My mum used oil clove to kill of the fish. I want to set it up with new fish, but think it smells of cloves.


I've got an 7" goldfish in my pond that has dropsy and is really suffering at this stage. I bought the clove oil at whole foods today, 15ml. If I put the fish in a bucket with water deep enough, how much clove oil should I add? Then how much vodka? Please help.


If you decide you need to put your fish down, please don't flush it down the toilet. I know they always seem to do that on the TV, but it is a terrible way to get rid of a fish.

Not only can it be potentially really ugly for the fish itself (remembering where that water goes!) but if your fish doesn't die it could become a pest in your local waterways. It could also have diseases that could infect your local fish.

I know it's unpleasant, but after using clove oil, you might want to make sure your fish is really dead. Sometimes the oil just makes them sleep a bit.

The best way of doing this is to lop off their head, but most people won't want to do that.

After that the best way to euthanize a potentially sedated fish is to pop it in the freezer for twenty four hours.

This means you don't have to worry about your fish suffering.


This is one of the reasons you should make sure you have a separate tank set up for your fish.

If you keep an aquarium of a few fish, you need to have this place where you can put them so they can be isolated from the rest of the tank.

This way you can make sure that they don't infect the tank with disease if they are starting to get sick, or can recover if they've been injured by other fish.

You can also put new fish in there as a quarantine, so they don't infect the whole tank with whatever was in their old one.

Fish euthanasia is not fun, particularly if you have kids who love your fish, so you should try to take care of them properly, so the need to do it doesn't come up very often.

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    • Clove oil, which can be used to euthanize a fish.
      By: Schlierner
      Clove oil, which can be used to euthanize a fish.
    • Vodka, which can be used to euthanize a fish.
      By: travis manley
      Vodka, which can be used to euthanize a fish.
    • An aquarium.
      By: Matthew Jones
      An aquarium.