Only methods reasonable to perform at home are included in this article. Other methods, such as electrocution and lethal injection, are difficult to perform humanely without training, and/or can harm the person performing them. [1] X Research source

Skip this step if you are using a method that does not involve drugs.

Some drugs, including MS-222, may not be effective in temperatures below 10ºC (50ºF). Euthanizing a large tank of fish is difficult, and requires measurements of oxygen and chemical concentration for best dosage calculations. [6] X Research source Ask a veterinarian to perform this if at all possible.

Do not eat fish killed this way.

Using alcohol to euthanize the fish has been described as dipping a person in gasoline to euthanize them. Don’t do it!

Shake one drop in water until milky, then add to the tank. When the fish is asleep at the bottom, shake and add another 13 drops per liter of water (50 drops per gallon).

No movement of gill flap for 10 minutes. (Usually following spasms 1 minute apart. ) No movement of eye when fish is rocked from side to side. Very slow heart rate. The heart may continue after death, but a strong, persistent beat means the fish is alive. If you do not see these signs within an hour or two, or if the fish wakes up again, add more of the drug. If you want to be certain the fish is dead, kill it with the physical methods below, or freeze it in ice water. These should not cause pain if the fish is deeply anaesthetized.

Unless you’re experienced with fish anatomy, practice on dead fish first so you can perform these quickly and without mistakes.

The larger the fish is, the less humane this death is. Even if you have a macerator intended for larger fish, it may cause suffering.

Fish species adapted for low oxygen conditions are more likely to remain conscious after decapitation. [16] X Research source

Alternatively, you can insert the knife behind the skull and sever the spinal cord and vertebrae. This “cervical transection” is less messy, but not recommended unless you have experience with fish anatomy.

You can use online resources to locate the most effective point to insert the spike, for various edible species. [19] X Research source