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The Puffer Forum • The Puffer Library » VIII. Euthanasia Options

VIII. Euthanasia Options

Author: Amy J, AKA Myaj

Euthanasia Options

*Author’s Note*
Some of these choices outlined in this article will contain methods which may offend some readers. They may seem excessively violent or gruesome, something you would never consider using on your fish… but imagine coming home one day and finding one of your beloved pets was sucked into a motor after a guard fell off, or attacked by a tank mate, and left mangled and helpless, with no hope of survival… yet still alive and suffering. In a situation such as this you may not have time to run to the drug store for some clove oil, or mail order some MS-222, and even if you do have the time, your fish will be suffering and probably dying while it waits. For some people, that is enough incentive to utilize one of the more “harsh” methods outlined below, for others, it is not. This decision is one that each fishkeeper will have to make on their own, no one can make it for them or tell them what choice is best. I highly encourage all readers to have some MS-222 or Clove Oil on hand in case such a situation should occur, and thus be able to avoid making that difficult decision. And of course, lets hope none of us has a need to use this article anytime soon.

Every fishkeeper will at some point face a fish that is injured or ill to a degree that indicates it should be humanely euthanized. It is not a decision to make lightly, but sometimes is necessary after all options have been exhausted.

Before deciding to euthanize a fish, be sure you have tried proper treatment, medication and maintained excellent water quality in a stress free environment to give it a chance to recover from whatever may be ailing it. Many fish recover well from things such as fins being ripped off, eyes gouged out, parasites, tumors and all sorts of ailments if they are given a chance and lots of TLC. The internet is a great source of information, and you can find many people who will have suggestions and support to help you through the process of diagnosis and treatment. If you are considering euthanasia due to not being able to provide the proper food, environment or tank mates for a fish, or if it has become too aggressive, it is better to contact local fish clubs, local stores and even online groups to find someone who is willing to adopt the fish and keep it appropriately.

The object of this article is to inform fish keepers of multiple options accessible to them when faced with this difficult decision. Different people will be more comfortable with different options, so several are mentioned for consideration. Often, this is a subject that is fiercely debated. This article is for informational purposes so fishkeepers can choose what they are most comfortable with if the situation arises. Remember when reading these options, there has been much testing on how fish “feel” pain compared to humans, with varying results. So, keep an open mind, and if the unfortunate event arises where you need to choose to euthanize a fish, make the choice that is most comfortable for you and your situation, while considering the best interests of the fish.

Let it be said first before we go into our options, that flushing a live fish down the toilet, drain or releasing them into a local water source or pond are not acceptable options for the conscientious fishkeeper. Flushing a live fish down the drain or toilet can result in the fish dying from poisonous waste treatment chemicals or getting stuck in the pipes and causing a clog. This is a cruel and slow death for the fish. Also, releasing a non-native fish into the wild is very dangerous to the environment and almost sure death for the fish itself, both very good reasons for why it is illegal to do so. Along the way, the fish may infect the inhabitants of a local pond or river with a disease or parasite they would have never encountered naturally, or throw off the natural balance and result in the irradication of a native species. There are many cases of lakes and ponds losing important species due to non-native fish being introduced. Please do your part to preserve our native species and their environments.

Methods for Euthanasia

MS-222 (tricaine methanesulfonate)

MS-222 is a anesthetic primarily used by researchers and veterinarians, which has recently become more available to the commercial public under the brand names Tranquil, Finquel and more. Mainly used by fishkeepers as a sedative or tranquilizer to immobilize fish for transport, capture, surgery or other handling, MS-222 can also be overdosed to achieve euthanasia when needed. To use MS-222, mix the dosage in a separate container of tank water, then add the fish to the solution. The recommended dosage for euthanasia is 10 grams of MS-222 per liter of water, allowing the fish to remain in the solution more than 10 min after visible breathing stops. Note: this product must not be used in animals to be used for food purposes. Do not add this product to any tank containing fish you do NOT wish to sedate or euthanasize.


• The fish dies quietly, first slipping into a sedated state before dying, which is limited stress on the fish and the handler.

• MS-222 is a good product to have on hand for emergency surgery and sedation


• As a chemical, MS-222 is more dangerous to use and have around the house than some other options

• It requires some handling of the fish (netting and placing in container)

Clove Oil (Eugenol)

Clove Oil (Eugenol) is commonly found at local drug stores as a toothache remedy. If it is not found out on the shelves in the toothpaste aisle, ask the pharmacist. Some pharmacies keep it behind the counter or can order it for you, or an online search will often find a mail order provider. Clove Oil is a local anesthetic which, when the fish is placed in a solution of water and the oil, will render the fish unconscious. It can be used for temporarily incapacitating a fish for surgeries, dental work, etc, and also for euthanasia if the fish is left in the solution for a longer period of time and a stronger dose. To euthanize the fish, place the fish in an appropriately sized container containing tank water. Determine how many cups of water are in the container, the recommended amount of clove oil to use is three drops per cup of water (1 litre = approx 4 cups). Premix the drops of oil with a little water in a smaller container and shake well, then add the shaken mixture to the container with the fish. After a minute or two, the fish will begin to swim uncoordinatedly, will tilt and turn, gently bump into things and will eventually turn belly up and float. At this point the fish is still alive, but unconscious, if it is placed in a container of tank water with no clove oil it will recover within a few minutes. If left in the solution for a longer period of time, it will die. Fish that are already weakened by an injury or illness will succumb to the clove oil faster than a healthy fish, however to be on the safe side leave the fish in the solution for an hour or more. Some recommend putting the container into a freezer once the fish is unconscious and allowing the water and fish to freeze solid to ensure death. Note: Do not add this product to any tank containing fish you do NOT wish to sedate or euthanasize.


• Process is clean, simple and quick, the fish (usually) quietly passes away with little to no visible struggling, so it is less stressful on the fish and the human

• Clove Oil is useful to have on hand for emergency or medical procedures on all your fish, not to mention human toothaches. However, it is worth noting that MS-222 is regarded as a more “safe” option when sedation, and not death, is the goal.


• Clove Oil (Eugenol) can be somewhat difficult to find, although most pharmacies do carry it

• Some people have reported the fish thrashing and appearing to be in discomfort when placed in the solution, this may be due to using a larger dose than is recommended here

• It requires some handling of the fish (netting and placing in container)

• It is not known for a fact if the fish is stressed during this method, though when used on healthy pufferfish for trimming teeth, they generally recover well, eating and behavior are normal within minutes

Freezing (sudden temperature shock)

Preparing a container of water in the freezer is the best way to use this method. Use a container large enough for the fish to fit comfortably in, filled with water. Let the water sit in the freezer until it is very cold, even starting to ice up, though within a degree of freezing is ideal. Then transfer the fish quickly into the bowl. The temperature shock will be enough to kill the fish instantly as the organs and systems will seize up from the sudden cold, though transferring the container immediately to the freezer for several hours is a good fail-safe.


• If done properly, the fish will die quickly

• Ice cold water is generally easily acquired


• It requires some handling of the fish (netting and placing in container)

• The handler must put the fish into the water and watch it die

Freezing(slower method)

Place the fish in bowl of tank water, add some ice cubes and place it in the freezer. The fish’s cold-blooded body cools to surrounding temperatures and shuts down, it will not fight to stay warm and circulate blood the way a warm blooded animal’s system would. The fish should be left in the freezer for at least 24 hours to be sure it is completely frozen, though it should be dead much sooner. There is some debate on how much stress the fish goes through during the temperature drop. Some studies have shown tropicals undergo more stress while cooler/cold water fish ease into a less stressful, dormant stage before death, due to their natural ability to handle cold water.


• Freezing to death is considered to be relatively painless, though studies on pain in fish are inconclusive

• The actual death of the fish happens behind closed doors, out of sight, so there is less stress to the fishkeeper

• Nearly everyone has a freezer available at all times, so there is no running around trying to find products

• The fish is in a dark, quiet environment that should help minimize stress


• The death of the fish is quite drawn out as they slowly freeze

• It requires some handling of the fish (netting and placing in container)

• There are stories of frozen fish coming back to life when thawed, however this seems most prevalent in cold/cooler water fish such as bass, goldfish, etc who are designed by nature to survive freezing conditions

Saltwater/Boiling Water Dip

Placing the fish in boiling water, water with a very high concentration of salt (at least one cup of salt per gallon of water) or a combination of boiling salt water, will euthanatize a fish immediately or quite nearly immediately.


• The fish dies very quickly upon contact with the water

• Everything needed (water, pot, stove, salt) is usually on hand, so no running around looking for products


• This option may be stressful for the fishkeeper, as many do not feel comfortable with the thought of putting their fish in boiling water

• The fishkeeper must place the fish directly into the water and witness it dying in front of them

• There is question of how painful it is for the fish, and how quickly they die

• Caution must be used to prevent injury from boiling water and steam burns

Beheading/Spinal Separation

Using a sharp knife or cleaver to remove the head or separate the spine will also quickly euthanize a fish. The cut must be made quickly and cleanly, causing death, not a mere injury, with the fish being taken out of water and dispatched as quickly as can be safely done. If done properly, there may be some twitching and flapping from the fish, most of this is due to nerves but there are some tests that show brain activity may last for a few seconds after decapitation.


• There is no question about if the fish is dead or alive like there may be with other methods

• It is over relatively quickly or even instantly if done properly

• Most people have a sharp knife available, and many have fisherman friends who are familiar with quickly be-heading fish


• A somewhat gruesome procedure that some people can not stomach

• The head may be difficult to remove with one clean stroke, so follow up “sawing” action may need to be used if the first cut fails, the fish will likely be alive for this

• The fish will need to be removed from the water and held down, so for those moments it will be stressed, gasping for air and likely struggling

• If not done properly, the fish may suffer longer as they bleed out or the person struggles to complete the task

• Caution must be used with any sharp blade to avoid injury to the person

Sharp Crushing Blow

A sharp blow to the head of a fish with some sort of club or instrument (hammer, rock, etc), or swinging the fish hard and smashing it into a surface (wall, floor) to crush the skull and brain has been used for decades as a way to dispatch a fish. Results will vary depending on the accuracy and strength of the blow, the object used and the size/type of fish. Often it may take several blows to kill the fish, and sometimes the fish may only be stunned, and not dead, requiring further efforts. This method is similar to beheading, requiring the fish to be taken out of water and handled, only generally with less control and accuracy, which could lead to poor results.


• This can be done just about anytime, anywhere, though any bystanders will likely not appreciate seeing it done

• Possibly a better option for larger fish than some others, due to their size limiting the efficiency of other options


• Death may not be instantaneous, and may require several blows before the fish is completely dead

• This is rather gruesome and stressful to fish and handler

• The fish may only be stunned, with the handler not realizing it, thus suffering more than necessary

Blender/Garbage Disposal

This method is best done with the blender or garbage disposal running before the fish is dropped in, and only works on smaller fish. Dropping the fish in, then turning on the blades generally will only result in the blades lodging in the fish and bashing it around, a very unpleasant death. If the blades are running at full speed when the fish is introduced, they cleanly chop it into several pieces, killing it quickly.


• Method is very quick

• Blenders and garbage disposals are common household items


• Very stressful to fish and handler, fish will be stressed and struggling while being carried to the device and dropped in

• Useful only for smaller species who will fit easily into the blade area of the blender

• If blades are not sharp, they may not cleanly chop the fish and jam up instead

• Due to the possibility of diseases and parasites, there is risk in washing it down the drain or using a blender that will be used to prepare human food

• Care should be used around any blades, especially moving ones

Veterinary Euthanasia

While not common, it may be possible to have your veterinarian euthanize your fish, or supply the anesthetics. This may involve adding a compound such as MS-222 to the tank water or injecting an anesthetic directly into the fish. This option may be the best one for larger fish that pose a challenge when it comes to applying other methods of euthanasia.


• The fish dies quickly, and painlessly

• If a solution is added to the water, the fish does not need to be handled extensively

• Professional instruction is provided, or it is done by the professional themselves, which is easier and more reassuring for the fishkeeper


• It may be hard to find a veterinarian who will handle this procedure or supply the anesthetic

• The substances used and the service provided may be expensive

• These substances can be harmful and should be handled only by professionals or very carefully, with proper disposal of gloves and other equipment afterwords

Disposing of the Deceased Fish

Disposing of the body of the fish is especially important if there was some sort of disease or illness that led to the euthanasia. Suggested disposal methods are wrapping the body well in plastic (such as resealable bags) and placing in the garbage, or by burning.

In Conclusion

When choosing to end the life of your fish, try to make the best decision you can. The fastest, least stressful way is often the best for the fish and your conscience, though different situations will affect which method you choose. Make an educated decision and research any questions you may have on the various methods if you are not comfortable with something about that option.

Good luck and happy fishkeeping!