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Fish & Visitors Smell in 3 Days...
Feb 27, 2007
New Hampshire

First, I did not plan on having this Topic become my first article; however, I have seen many posts ask about, ‘How do you humanely euthanize a fish?’ Many of those same threads provide differing opinions on not only the methods to employ but also to its necessity…

Myths: “Fish can’t feel pain right?”
This is a very common question, and myth, but more often than not I have found that most are simply looking for some sense of reassurance that what they are proposing to do is ethically/morally okay. The truth is, however, that of course they feel pain. Fish have an intricate nervous-system, but we often don't readily see the signs of distress because fish lack the facial responses and expressions we readily associate with pain and fear typical in most animals. The reality is, if you're observant to the signs, many fish noticeably exhibit either behavioral or physical signs of affliction when they're distressed or in pain (ie. vigorous and often violent movements; color-shifts, often fading or paling in nature; and changes in normal social and other behavioral activities are all clues to their distress). Many of these same symptoms we actively use in our hobby to discover wounds, diseases or other ailments earlier than we perhaps would otherwise.

What is it, and Why do it?
euthanasia (yū'thə-nā'zhə, -zhē-ə) n.
Greek, meaning “Good Death”.
“Euthanasia is the practice of ending the life of a human or animal who is incurably ill in a painless or minimally painful way, for the purpose of limiting suffering. Laws around the world vary greatly with regard to euthanasia, and are constantly subject to change as cultural values shift and better palliative care, or treatments become available.

- Reference: Wikipedia

How do I know if my fish needs to be Euthanized?
Reasons for Euthanizing a Fish –
  • Irreversible Disease - Cannot be treated, such as Cancer
  • Major Injury - Fish cannot survive on own
  • Suffering – Non-treatable ailment (i.e. In some cases; old age)
  • Culling
NOT Reasons for Euthanizing your Fish -
  • Fish outgrows it’s environment, or is inappropriate for your setup
  • Fish becomes aggressive towards other tank-mates
  • Lose interest
  • Moving, or desire to change your tank
  • Any other reason given that is correctable or the cause of the owner
Methods Commonly Approved:
I would like to preface this section simply by saying that many methods are in use and that most are controversial (as is the very notion of Euthanizing), but I have only tried to list those methods deem ‘acceptable’ by most and would be considered common practices. Certainly others exist…

Correct Approach is to place a bowl of water into a freezer and let stand until a thin crust of ice has formed. The ice should be sufficiently formed to require one to break threw the surface. The goal is to ideally reach a Fahrenheit temperature of 29 degrees (or less). Once achieved, a fish may be placed in the bowl. Nearly instant, it is a very quick and efficient method by most accounts.

Alcohol – Is not an approved method on its own (See Clove Oil).

Clove Oil – Perhaps the most commonly employed method and very economical. This method is an anesthetic-like approach in that the Clove Oil is used first to place a fish under sleep. Ethanol-based alcohol is then utilized to euthanize the fish after the fish is unconscious.
- A Common Mistake is to mix both the clove and alcohol together, or to use a non-clear, non-grained, alcohol (colored alcohols, such as whiskeys, are not allowed to fully ferment and are thus not approved due to lack of ethanol concentrations).
- Alcohol used should be clear in nature and grain-based (commonly known as ethyl or ethanol) such as a Vodka. Although effective, vodka is still diluted, and the concentration of ethanol is deliberately reduced (25% alcohol of the total water volume is typically recommended).
- Note: Clove Oil is also lethal in 5-6x the recommended concentrations (ie. 50-60 drops per US Gallon). Also, please note; it is recommended that the fish is first placed under prior to spiking the concentrations to lethal doses.

Clove Method How-To: (Fish up to 3”)
1. Using a small clean container, filled with tank water, add approx. 1 drop of clove oil per 24oz.*, and shake vigorously. The clove oil must emulsify (will turn the water a milky white). *Remember the amount of water you use (needed for alcohol concentration below).
2. Add the fish, and check back in about 10-15 minutes. If the fish is still swimming occasionally, pre-mix a small amount of clove-oil and add this to the container. Wait again.
3. Add 20-25% volume of grain alcohol. For example, if the fish is in 8oz (240ml) of water, add 2oz (60ml) of vodka.
4. Check the fish carefully after 20 minutes. If there is no sign of gill movement after a minute, the fish has expired.
*(Fish over 3”+) Follow the above instruction, but increase the Clove Oil concentrations to 10 drops per US Gallon (or 1 drop per 13oz).

- Reference: Wisegeek & Aquaria Central

Anesthetic – By far and away the most humane is through the use of anesthetics. Many of our LFS and on-line aquarium providers offer this solution. The most commonly used product is commercially named, Finquel (Link for convenience: Finquel Aquatic Anesthetic). From this, any of the Methods already discussed may be used, or one can simply apply the recommended dose, wait for sedation, and then spike with approximately 3-4x the dose. The effect is the fish calmly falls to sleep, and the increased concentration simply stops their heart. No suffering.

Methods NOT Approved:
First, let me be perfectly clear that these are NOT Methods of choice, nor offer a humane approach! Secondly, I am listing these so that I can be clear on the intent for this Article, and dispel ANY notion that these can be considered humane.

Frankly, as an Aquarium Hobbyist, your first obligation is to the animals we have taken the responsibility to care for, and as such, I feel it is something we have willingly accepted the responsibility to perform in the most humane manner possible. ‘Until death do us part’, if you will.

Club or Smash – I could also include the “Blender” approach here as well for it’s shear brutality… For most, the potential loss of a pet is very traumatic, and ensuring the quick and stable hand required for this approach is hopeful at best, especially to those not only unwilling, but (hopefully) novices to this barbaric approach. Simply, too many things can go wrong, and with so many other humane approaches available there is simply no excuse to employ this method.

Flushing (Live) Fish – What can I say? Well, first off, this will not kill your fish – At least not quickly or painlessly. Taking a living fish plopping them into a bacteria infested, chlorinated toilet bowl, and pushing a lever to flush a fish simply guarantees two things: 1) That the fish will suffer a long time while it is slowly suffocated and poisoned, and 2) it ensures that the fish is “Out-of-sight, and Out-of-mind”.

Freezing (Live) Fish – There is a right and a wrong way to “Freeze a Fish.” Fish are very sensitive to temperature changes, and a few degrees can easily send a healthy fish into shock (See: Methods Approved for the ‘Right’ procedure)
Wrong Approach is to simply place an ailing fish into a bowl of water and place them into a freezer. Many employ this technique as it ‘appears’ placid. However, the reality is they are freezing to-death much like you or I would. The thrashing and ‘signs of agony’ are absent because their metabolism is shutting down, their bodily functions begin to slow dramatically, and blood recedes into their core in their futile attempt for survival. Eventually, they slip into a sleep, and die. How long does it take to make ice?

Alcohol – Is not an approved method on its own (See Clove Oil). The cause of death is by alcohol poisoning.

I hope this article can be used as a resource to more humanely address this issue. The When and Why I will leave largely up to you...
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