Euthanasia

This is a delicate subject to deal with. For the good of the tank, or the good of the fish, or sadly the good of the aquarist, there will come a time when the greater good outweighs the individual and you must put and animal down. This may be due to a contagious disease, a fish in its death throes suffering needlessly, or for a personal reason of the hobbyist who cannot house a specimen(s) such as excess fry or the culls of a bad pairing. These cases are far and few between, but they do in fact arise during our hobby and it is important to know how best to deal with it. Science is not exactly sure if fish can feel pain, or they simply react to stimuli, but one thing is sure. It is difficult for we humans not to empathize with our pets and even if the methodology doesn't matter to our fish, it does matter to many of us. There are two preferred methods of humanely euthanizing a fish. There are in fact several other methods that are highly effective, however they often involve massive trauma which cannot be more humane than the methods I will describe.

Method #1 is the use of clove oil. There are products sold today that are designed for the purpose of euthanizing fish and these all contain clove oil. This method simply anesthetizes the fish unconscious so deeply its heart stops. This is very similar to how many states perform Lethal Injections today. I have a hard time finding clove oil in my rural area, so I prefer the second method which is FREE!  There is a product now being sold that is specifically for euthanizing fish, it contains mainly

Method #2 my preferred method! Fish are cold blooded animals, so when their environment is warmer they are more active and as it cools down they become less active. If their water temperature drops far enough they begin to enter a hibernation-like state. This state is how these animals survive temporary cold spells in nature. While in this state fish can appear almost dead on a life monitor due to their metabolism being near zero, fish cannot survive freezing solid like frogs can.  So when temperatures drop low enough for a long enough period the animal simply expires.  Recent discoveries indicate that fish may still feel pain while in the hibernating state.   It's questionable whether or not they are aware of it with their metabolism near zero however.

For smaller fish you can zip-lock them in a freezer bag with just enough water to cover them and place them in my freezer for an hour or two. The time length depends on your freezer and the size of the fish, but once it is frozen solid is has expired. You can also use a bowl if your significant other doesn't mind such use of kitchen utensils, or like myself you've acquired your own for the purpose. Using a bowl works well for culling a group of fry.

Method #3 I call the "Redneck" method because it involves violently throwing the fish against the floor head first as hard as you can.  This method is pretty instantaneous and probably doesn't allow the animal to feel pain, however you should be aware that with larger fish they probably will survive this and suffer as a result.

 Method #4 is called "Plithing"  by inserting an ice pick like rod into the brain or simply using a sharp fish and decapitating the animals head.  This method is violent and messy and I cannot recommend it. 

Method #5 is called "Cycle of Life" where the fish is fed to a predator fish.   While there may be some pain involved, and is certainly stressful, it is also a very natural death.