© "Ren" Weeks
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___Fish differ from most household pets in that injuries and illnesses are typically treated out of the home without the assistance of a veterinarian. While this certainly makes fish keeping less expensive for the average hobbyist, and also allows for immediate treatment at the first sign of disease, it also means that there is little recourse for aquarists who can not heal their companion and must instead find a way to end its suffering.
___Much like medical treatments for aquarium fish, euthanasia is often a subject of heated debate among fish keepers. Until recently, when laboratory studies finally gave conclusive evidence that fish are very likely capable of feeling pain, euthanasia was an "anything goes" process that was often quite painful for the animals involved. Less refined methods resulted in lingering, painful deaths, and in some cases further injury without death.
___Current methods are imperfect, but generally thought to cause less suffering than earlier methods. Though the AVMA has a fairly limited (or perhaps limiting) selection of acceptable methods of euthanasia, there are a variety of methods employed by fish keepers with anecdotal evidence suggesting their effectiveness. This article will cover both the AVMA accepted methods, common but more controversial practices, and finally, which methods are decidedly inhumane or unacceptable.
AVMA Guidelines for Fish Euthanasia
___Presently, the AVMA accepts the following methods of euthanasia as humane for fish: pithing/brain destruction, CO2, injection of sodium pentobarbital, immersion in tricane methane sulfonate, immersion in benzocaine hydrochloride, immersion in 2-phenoxyethanol, anesthesia followed by decapitation/pithing, and decapitation w/pithing. To read about these methods in detail, click here. Clove oil, cooling, and other “DIY” methods are not considered to be definitively humane or acceptable due to a lack of research. However, for the casual fish owner who does not have access to proper euthanasia solutions, the methods below are supported by anecdotal evidence and experience.
Common Fishkeeping Methods and Procedures
___The following information details procedures for fish euthanasia that are considered acceptable, albeit with controversy. Please note that not all of the methods below are AVMA approved, and opinions within the fish keeping community are highly variable regarding the effectiveness and painlessness of each method. Use your discretion when trying a method, and follow the instructions precisely to prevent injury or recovery.
Destruction of the Brain - Pin Method (Pithing)
___The Pin Method of brain destruction, also known as Pithing, is an AVMA approved procedure that involves the insertion of a pin into the skull of the ailing fish, then destroying the brain. The benefit of this method is that it kills rapidly with minimal pain, save for the initial insertion, and does not make as much of a mess as the blunt force method. However, when done inaccurately, it can obviously be very painful, not immediately fatal, and traumatic for the owner. There is also added stress to the fish by removing it from the water. Please note that this method is not suggested for larger fish such as Koi, as it is not likely to be quick or fatal in a comparatively large brain.
- Isolate the fish to be euthanized in a small container where he will be easy to capture while you gather a paper or cloth towel, a sharp pin, and if desired, a sharpened scalpel.
- Once you have your supplies handy, carefully remove the fish from the water and wrap it securely in the towel, such that only the head is visible.
- As quickly as possible, insert the needle into the skull and "stir" rapidly, effectively destroying the brain. You will want to position the needle at the medial (central) "forehead" of the fish, similar to where one would use a captive bolt gun on livestock, as destruction of this region is thought to immediately stun the animal. Inserting from the back of the skull is more likely to merely paralyze the animal, as is the case with dissection specimens.
- After the brain has been destroyed, a secondary method such as decapitation may be employed if desired to ensure death.
___The Blunt Force method is preferred by some over the pin method because the destruction of the brain is so swift, immediate, and complete that it is very unlikely to make a mistake that will result in a lingering death; it is almost impossible to do incorrectly, which is a significant risk of the pin method. It is AVMA approved, and kills instantly. However, it is a violent, messy practice that can be very traumatic for the owner of the fish, and also has the added stress of removing the fish from the water. This method can be used, however, on larger species of fish with a large enough blunt object.
- Isolate the fish to be euthanized in a small container where he will be easy to capture while you gather a cloth or paper towel and large blunt object. For a small fish, a hammer or brick should be sufficient.
- Once you have your supplies, the fish should be removed from the water, wrapped firmly in the towel, and placed on a hard, solid surface. You may cover the head if desired, so long as you know its exact location.
- Using your blunt object, land one heavy, crushing, high-velocity blow to the head. If done correctly, this should obliterate the entire skull, including the brain, resulting in an instant death. Please note that the body may twitch following this method due to the force and violence of the blow. The fish does not feel this; its brain is gone.
___A preferred and AVMA acceptable method of euthanasia is to massively overdose on an anesthetic. There are several chemicals approved for fish euthanasia, though most are available only to professionals in the veterinary field. However, some products containing these compounds are available on the market for casual use as a sedative. A significant enough overdose of such a product should ultimately result in death, but as with Clove Oil, a prolonged exposure and significant overdose are key to preventing revival. Again, a secondary method may (and perhaps should) be employed to ensure death. The following instructions are for betta euthanasia using the product Finquel made by Argent Labs, which may be difficult to come by but can be direct-ordered from doctorsfostersmith.com. Detailed directions for sedative use and product information are available here.
- Obtain a small container with a lid and measure its volume in Liters when filled.
- Using the following proportion, determine the mg of Finquel for your container. This calculation uses a double dosage; you may use more, but less is not suggested,170mg/1L = xmg/xL
- Fill the cup to the very top with water from the tank. The higher the tank temp, the better; no less than 75 degree water should be used, If possible, slowly raise the tank temp to 82 through the course of the day of euthanasia.
- Dissolve the appropriate number of mg Finquel in the water by pouring and gently stirring.
- Remove the betta via netting or hand scooping and place in the solution. Lid the container, making sure it is full enough for minimal air space; this will force the betta to gill-breathe the solution.
- If no secondary method is to be employed post anesthesia, leave the fish in the solution for a minimum of 12 hours, with 24 preferred to be safe.
___An increasingly preferred method for many aquarists, immersion in a Clove Oil solution is less stressful on owners and fish alike if carried out correctly. It is more expensive than other methods, and does not cause an instantaneous death, but is a quick and theoretically painless killer; the chemical eugenol in Clove Oil has anesthetic and analgesic properties, and is used in its purified form to anesthetize fish during surgeries. Thus, like any overdose of anesthetic, death should occur peacefully. However, a lack of research and concrete, scientific evidence of its painlessness means that this method is not AVMA approved and not guaranteed to be humane. Also please note that unless a massive overdose is delivered for a prolonged period of time, there is a chance of revival, so a secondary method may be employed.
Update: New research suggests that Clove Oil can be used humanely for euthanasia. You may read the primary research article here.
- Purchase a small bottle of clove oil from a health food store or pharmacy. You want to select the kind intended for dental pain, not the scented oil. The bottle is usually expensive, but can be used at least four times depending on how you wish to carry out the procedure.
- In a small container with a lid, scoop up enough water from the aquarium to fill roughly half of the container. In another small container, scoop up the fish to be euthanized with a lesser quantity of water.
- Add clove oil to the fishless container with the lid. Although a few drops will probably suffice, the speed of the unconsciousness and death and the chance of revival relate directly to the concentration of the clove oil in the water. I personally suggest ¼-½ bottle for an almost instant death for a small fish; if you use less, you must incorporate a secondary method. Note that larger fish will need greater quantities of clove oil, as will multiple fish being euthanized simultaneously.
- Once the clove oil is added, replace the lid and shake vigorously. You will want the clove oil to be completely dispersed in the water, creating a cloudy yellowish colloid. Do NOT use Vodka as an emulsifier; alcohol will cause un-needed pain until the clove oil takes effect, and is non-essential to the process anyways. There is a method that uses Vodka after the fish is unconscious as a secondary culling method to ensure that there is no revival, but never, ever add the vodka prior to unconsciousness.
- When you are confident that the clove oil is well dispersed, scoop your fish into the container. You may pour him and the contents of the holding cup in, but this will decrease the concentration of the clove oil, so do so at your discretion.
- Monitor the fish closely. Depending on the size of the fish, amount of water used, the temperature of the water, and concentration of clove oil, you should see movement end within seconds. (Using the ¼-½ bottle method I have suggested, you should not observe any prolonged thrashing or struggling as with the "drops per gallons" method.) Gill movement typically halts shortly thereafter.
- It is possible for an unconscious fish to regain consciousness if the concentration of clove oil or time in solution were inadequate. As such, I personally suggest leaving the fish in the solution until its color fades, eyes glaze, and slime coat starts to shed. With the suggested concentration, there should be no recovery.
- If desired, you may destroy the brain of the fish or use any secondary culling method for extra certainty once the gill movement has stopped for at least one hour, but it should not be needed if you leave him in the water until he is obviously dead based on the signs listed above.
- Note that the warmer the water used, the quicker the metabolism of the clove oil, and thus the quicker the death. The day of the euthanasia, you may want to raise the temp in the fish's tank to the higher range of acceptable temperatures for the species (ie. 82-84 for tropicals) to help speed up the process.
___The Shock method is one of the oldest methods for euthanizing tropical fish (it is not acceptable for coldwater fish), and involves rapidly immersing the fish in a bath of water just above freezing in temperature. The theory behind it is that the sudden and severe temperature fluctuation will put any tropical fish into shock, killing it shortly thereafter or stunning it enough that a secondary method of euthanasia can then be employed. It also is said to reduce the sensitivity of nocireceptors (pain receptors). Please note that this method is not proven immediate nor painless, though it is fairly quick and, based on our present understanding of shock, most likely only briefly painful until shock sets in. It is recommended against by the AVMA.
- Place a container (with lid) filled with water and adequate for the size of your fish in your freezer with a glass or probe thermometer. Periodically monitor the temperature of the water.
- When the water has reached a range of 33-40 degrees, the lower end of the range being preferable, remove it from the freezer and collect the fish.
- Remove the fish from its water and plunge it immediately into the cold water. Do not acclimate or put it in a separate container. Place a lid on the container lest the fish thrash and jump, but most owners report an almost instantaneous paralysis.
- Leave the fish in the cold solution until gill movement halts and color fades, or alternately, destroy the brain once gill movement halts and the fish appears "paralyzed."
- Note that this method is unacceptable for coldwater fish, as it will more likely push them into a state of hibernation that they may later recover from, still sick/injured with the additional stress of the temperature shock.
___CO2 is a common medium of euthanasia across the species board, as it replaces oxygen in the blood, resulting in a very rapid death IF introduced in an air-tight system in high concentrations. The AVMA suggests CO2 euthanasia as a primary method of euthanasia of aquarium fish. However, it is extremely difficult for laypersons to create or locate the kind of system required to properly euthanize a fish. Ideally, a pressurized CO2 tank could be used to disperse a high concentration of CO2 directly into the water in a closed system. However, some sites suggest that a sealed container and a few CO2 tablets do the job just as well - though not nearly so rapidly. Opinions are very mixed on this "DIY" method, and many sites consider the use of “seltzer“ tablets to be inhumane due to potentially painful additives in said tablets.
___A compromise seems to involve building a makeshift CO2 bubbler, which involves one container with a tightly fitted lid and snug-fitting air line tubing linking it to a second small lidded container with some kind of fine matrix bubbler on the opposite end of the tubing. The suggested procedure is to produce CO2 through whichever means are most available in the first chamber, allowing the air line tubing to funnel the produced gasses into the second chamber, where it will be forced through the bubbler into the water containing the ailing fish. Instructions on another method of building a CO2 bubbler can be viewed here. Reviews are also mixed on the speed and effectiveness DIY CO2 bubblers.
___The problem with CO2 is that it must be employed in a massive dose for a prolonged period of time for success, or there is a high risk of recovery. Because of this, most aquarists will use CO2 to induce unconsciousness, then employ a secondary method such as destruction of the brain. It is strongly suggested that even with a functional home made CO2 system, additional steps be taken to ensure death rather than mere stunning. ((I lack detailed instructions for this method as I have never tried it and can not readily find the information. If you have used CO2 to euthanize a fish and would like to share instructions on how to do it using readily available supplies, please PM me)).
___Some prefer the all natural approach to euthanizing fish: feeding it to a predator. Depending on the species and feeding habits of the predator, this can be a nearly instant, relatively painless process. In the case of fish who are badly injured or severely deformed, it is probably one of the fastest, least painful, and least wasteful methods of disposal. However, in the case of a sick fish, there are some serious flaws with this method. For example, if you are feeding a smaller fish to a larger predatory fish, any diseases or parasites may be communicable. When feeding fish to reptiles and amphibians, the species of the fish must be acceptable (ie. Goldfish should not be fed to ACFs as they can prevent the proper metabolism of vitamin B), and the risk of spreading parasites or infection is almost equally high. Few pet owners own birds or mammals with a fish-based diet, and most terrestrial species willing to eat a fish will make it a slow, painful, messy process. In other words, feeding out a fish as a method of euthanasia is acceptable under only a few highly specified conditions - making it risky, if not controversial.
___Some methods of fish "euthanasia" are inherently cruel and completely unacceptable - though the lacking legal status of fish unfortunately makes most culling methods legal, so cruel practices subsist even on an industrial scale. Any practice that results in undue stress, pain, prolonged death, or further injury prior to death should never be employed, regardless tradition or social acceptance. While improper methods are almost endless, some of the most commonly misused methods of culling include flushing, freezing, suffocation, boiling, bleach, alcohol, and ammonia. All of these methods result in a death probably worse than dying from natural causes due to disease or injury, and should be avoided (also, never promoted). There will not be instructions on these methods provided in this section. Rather, the reasons for why the method is inhumane will be discussed.
___Flushing involves washing a still-living fish down the toilet, or occasionally a garbage disposal. Many uneducated owners prefer this method because it is "out of sight, out of mind," and assume it results in rapid death. Unfortunately, flushing is not quick, nor is it painless or stress free. Fish often sustain further injury being washed down the pipes, and then linger before dying in agony in a vat of human waste that awaits them in the septic system. Worse still, some become trapped in the pipes, where they can survive for hours providing sufficient water is in the system, in fear and stress, being exposed to chlorine and waste. This is perhaps the cruelest possible method of euthanasia because it is so slow, and should never, ever be used to euthanize any fish.
___Freezing is considered inhumane for both cold blooded and warm blooded animals by the AVMA. Due to the nature of cold blooded animals like fish, a slowing rather than cessation of bodily processes at low temperatures may allow the fish to remain alive as cell crystallization occurs - an agonizing death. Water, especially at the temperature tropical fish are kept in, freezes slowly in normal refrigeration units, and the slow speed of the temperature drop almost guarantees that the animal will not merely go into shock and lapse into unconsciousness. It is argued that flash-freezing in liquid nitrogen or a rapid cooling system induces immediate shock much like the shock method discussed above, and may be acceptable as a form of euthanasia. Many fish stores and fish owners with the appropriate resources do employ rapid freezing as euthanasia, and it is legal. However, for the sake of this article (and AVMA standards), it is considered inhumane.
___Some fish keepers argue that if cold-induced shock is acceptable, heat-induced shock via boiling should be equally acceptable. However, cold-induced shock, while potentially initially uncomfortable, does not create the massive tissue damage and agony of being cooked alive. Boiling is inherently cruel in every regard, creating massive burns to the external and internal organs, and is not always a rapid killer. Even quick immersion results in a painful and oft times prolonged death, and is completely unacceptable for all species. Regardless of its legality and common use, it is also suggested against for aquatic invertebrates, many of which have primitive nervous systems and may be capable of feeling pain (the science is still out on whether or not invertebrates feel pain, but they do respond to their surroundings via the sensation of touch, so it is highly suspect that they must).
___Suffocation is a common method for fish euthanasia employed by fishing boats and other industrial fishing operations, but some owners also believe it to be acceptable. In reality, suffocation for a cold blooded animal is an extremely long and drawn out process, taking minutes to hours depending on the temperature, due to the slow oxygen metabolism of ectothermic species. For fish, suffocation also involves removal from the water, resulting in undue stress, drying and scraping of the tissues, and in the case of anabantids, a slow, painful death by complete dehydration. Suffocation is comparable in terms of pain, fear, and distress to drowning in mammals, and should never be employed, regardless of its legality or common occurrence in industry.
Decapitation w/out Destruction of the Brain
___Decapitation was once a common method of euthanasia for cold blooded animals, as it is highly effective and comparatively quick in warm blooded animals. However, because oxygen consumption is slower in ectotherms, there have been many documented cases of the heads of reptiles retaining consciousness (and even biting) post-decapitation. We can therefore infer that coldwater fish in particular likely maintain consciousness after decapitation. Thusly, the brain MUST be destroyed after decapitation if you employ this method; decapitation without destruction of the brain is unacceptable,
___Many novice fish keepers have used caustic, toxic chemicals such as bleach, ammonia, or alcohol to euthanize fish. It is true that these substances will kill fish. However, unless massively concentrated, death is not quick. More importantly, death through these methods is inherently painful due to the caustic nature of such chemicals. Massive chemical burns of the body and gills are inevitable, and death is often lingering. Please never use any harsh chemicals to euthanize your fish.
___Proper euthanasia method remains a contentious issue amount fishkeepers. Because many of the AVMA approved methods are not available to the public, and aquatics vets are few and far between, we are forced to make difficult decisions regarding the lives - and deaths - of our beloved companions. This guide has offered several possible methods for euthanasia, as well as several which should never be employed. It is now up to you as the fish's guardian to determine which will provide the most expedient and painless death. Remember, suffering from illness is a cruel enough fate; please euthanize humanely so that suffering does not occur in death.
World Cichlid Forum - See Phil's Post
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