How do I euthanize my fish?

The Merriam-Webster Online Dictionary defines Euthanasia as follows: the act or practice of killing or permitting the death of hopelessly sick or injured individuals (as persons or domestic animals) in a relatively painless way for reasons of mercy.

As a fish keeper, there may come a time that you need to euthanize one of your fish. In this article we will look at the various methods available to us. I will not recommend any of the methods as I have not yet come to the point that I needed to euthanize a fish. While I won't be recommending any of the methods I discuss, there are methods that I will suggest you not use for various reasons.

Toilet Flush - Not recommended
This is probably the most common way a lot of beginning fish keepers use to euthanize their fish. It is a misconception to think that flushing a fish is actually going to kill it relatively painlessly, which is what we are trying to do. Flushing your fish will subject it to various things in the sewer system, none of which are very pleasant to think about.

Hit it on the head - Not recommended
While this method can accomplish our goal, it is very difficult to do on most fish. To be effective you need to strike the fish in the head hard enough to kill it, all while keeping hold of it. Otherwise you may end up dropping the fish on the ground thereby losing it, only to find a crispy critter at some point in the future.

Cut the head off - Not recommended
For the fish keeper that is also a fisherman this method may be acceptable as they have the experience to do it. I don't like this method for a variety of reasons. It can be gory. It can result in bodily harm to the fish keeper and I think that there are more humane methods than this.

Freezing the fish
This method involves putting the fish into a container that will fit into the freezer and that you are willing to discard. Put some water into the container and then introduce the fish. Put the entire thing into the freezer. There seems to be some debate as to how long you need to leave the container in the freezer but I would suggest leaving it for a minimum of 8 hours. Do not "check in on" the fish during this time. If you do, it could cause the process to take longer. Since the goal of euthanasia is to be relatively painless, I don't think I will be using this method when I finally do need to euthanize a fish. I say this because I question how painless freezing to death is.

Sudden temperature change - colder
This method is different than the one mentioned above. Instead of putting the fish into the container then putting it into the freezer, we will first get the water in the container very cold. This can be accomplished in a couple of different ways. The easiest is to fill the container with ice (much like making yourself a drink) then put in very cold water from the tap. Let it sit for a few minutes and then your ready to use it. Another way is to put some water into a container then put it in the freezer. The goal here is to get the water as close to freezing as possible with out actually freezing it. Once you have your container of very cold water (using whichever method you prefer) simply put the fish into the water head first as quickly as possible. The shock of the sudden drop in temperature should kill the fish almost instantly. This method is not suggested for coldwater fish.

Sudden temperature change - hotter
Use this method for coldwater fish instead. For this method we need to get some very hot (not necessarily boiling but over 120 °F) water into a container and then drop the fish head first into the container. Again the sudden change in temperature should kill the fish almost instantly. One side effect of this method is the fish keeper may feel like he/she is cooking a beloved pet. Use this method with caution as it can also cause injury to the fish keeper.

Alcohol
I'm talking about the really pure stuff like Jack Daniel's or vodka not a beer or a wine cooler. Put enough alcohol to cover the fish into a container and drop the fish in headfirst. The alcohol will cause almost instant paralysis and respiratory failure in the fish, which accomplishes our goal of a relatively painless death. Only use this method if you are of legal age to posses the alcohol or have someone that is of legal age with you while you are using the method.

I'm sure there are other methods out there that may work just as well as the ones mentioned above. As fish keepers we may not want to euthanize a fish but I believe euthanasia is better than letting the fish live in pain if it is obvious that it will die anyway. If you have found a quick and painless way to euthanize a fish that is in pain then you are a better fish keeper and a better person for it.