Euthanizing our pet fish is obviously something none of us ever want to have to do, but sometimes it's the kindest thing if the fish is suffering and has no hope of recovery. There are lots of ways people have come up with for euthanizing a fish, but the most humane method is by administering an anesthetic overdose. This can be done with MS222, Finquel (a version of MS222), or simple clove oil (eugenol). Finquel or MS222 can be purchased online and clove oil can be found at many natural foods stores in the health and beauty section.
Items You'll Need:
-Finquel, MS222, or clove oil (in these directions, I use clove oil).
-A container large enough to hold the fish.
-A small container with a lid, like a baby food jar.
-A couple of hand towels.
-A ziploc bag.
-An air pump, some airline tubing, and an air stone.
1. Fill the large container with dechlorinated water that matches the tank water in temperature and pH. You can actually just use water directly from the tank if you'd like; this is what I prefer to do.
2. Next plug in the air pump and place the air stone in the water.
3. Then fill the small jar about halfway with water and add 7-11 drops of clove oil. The water and oil will resist mixing, so you have to cap the jar and shake it until it's well mixed. You'll know it's well mixed when the water in the jar becomes very clouded.
4. Pour this water and clove oil mixture into the container.
5. Then gently lift your fish into the container. The fish should not have a strong negative reaction to the clove oil, but sometimes they will open and close their mouths rapidly at first. Soon though, the fish's gill movements will begin to slow down and it will start listing to one side. After about 10 minutes, gill movements should have slowed to a stop or at least to a near-stop. If this hasn't happened, just add a few more drops of clove oil after mixing it well with water.
6. After you have seen no more signs of life from the fish for five minutes, leave the fish in the clove oil for another 10 minutes at least just to make sure it has indeed passed away. After this, you can remove the fish and place it into a ziploc bag. What you do with the remains is completely up to you; some people bring it out to the trash bin, while others bury it in their yard or under a plant.
I hope you'll never need to use this information, but if you do, at least now you know the humane way to euthanize a fish so you can allow your pet to pass away with as little stress as possible.