There comes a time in every aquarist's life when a fish that can no longer recover from disease or injury must be euthanized. This is no easy task but it can be done humanely and peacefully without stress to fish. Acceptable Methods Clove Oil & Vodka
1. Add tank water to a measuring cup or other container. Measure the amount of tank water you add to the cup or container and make a note of it. Place the fish in the container. If the fish is in a clear container, place a dark towel around it to calm the fish.
2. Fill a small, clean jar or bottle with tank water, leaving some room at the top. This might be a baby food jar or pill bottle. Put 1 drop of clove oil in the jar or bottle, cap and shake vigorously. The clove oil must emulsify, turning the water milky white.
3. Gently pour about 1/4 of this emulsified mixture into the fish's container. The fish will begin to fall asleep. Let the fish be for about 10 minutes. The fish should be resting on the bottom by then. It will look dead, but if you watch closely its gills will be breathing once every few seconds. If after 10 minutes the fish is still rising off the bottom swimming intermittently, retrieve the jar or bottle of emulsified clove oil, re-shake, and add the same dose to the fish's container. Wait again.
4. Once the fish is asleep on the bottom, add 20-25% white grain alcohol such as vodka. For example, if the fish is in 8oz of water, add 2oz of vodka. Let the fish stay there for at least 20 minutes.
5. Check the fish carefully after 20 minutes for any gill movement. If there is no gill movement over a 60 second period, the fish has expired. Freezing
Freeze water in a bag or container untill the water is slushy. Place your fish in the water and continue to freeze it. The fish's metabolism simply slows way down and eventually stops. Unacceptable Methods:
Unacceptable methods of euthanasia are: boiling, chopping, removing the fish from water, using a seltzer tablet, slamming, pithing, decapitating, or flushing down the toilet. These methods are slow, torturous, stressful and violent. Please never use these methods to euthanize your fish.
Hopefully you will rarely have to perform this task, but when you do, it is at least comforting to know your fish does not have to suffer.