I’m so sorry I took so long to get to this question. The same day you sent it, I found out my boy Bucket had dropsy and I didn’t have it in me to write out the process or take pics for a guide. :c
But, I’ll write it now. Deciding to euthanize a fish is always hard, and never feels good. The description of the euthanasia/techniques below may be upsetting to some so it’s going under a read more.
The best way for a home aquarist to euthanize their fish humanely is clove oil. Freezing is completely inhumane and very painful- as the fish is conscious through most of it. Vodka and other alcohols are the equivalent of putting them in a gas chamber- it is neither fast nor painless.
The other painless option is blunt force trauma- which is fast and painless but can be traumatic for any owner. If you have the fortitude to do this, by all means do it. Otherwise… don’t even consider it. I hesitate to even describe the act here because I don’t recommend it to virtually anybody, seeing as there is room for error and error with this method is absolutely traumatic. But vaguely put, you can use a blunt object the instantly kill the fish if they are small enough.
But back to clove oil. Clove oil (aka eugenol) is an oil commonly used to relieve toothaches. It is an anesthetic and numbs the pain. But pure clove oil is also an anesthetic for fish. It can be used to put them under for surgery (though vets often use other chemicals for this). It works to make all fish unconscious. Essentially, euthanasia with clove oil is giving them a massive overdose of this anesthetic. They go under peacefully, and die while unconscious.
As a preface, if used incorrectly clove oil can cause your fish to panic. It is very important to get him to go under peacefully BEFORE ADDING THE OVERDOSE OF CLOVE OIL. Otherwise it will cause him/her to freak out and quite possibly jump out of the container, traumatizing both you and the fish.
So your tools will be the following (I am writing this as a reference for euthanizing bettas, so the measurements are for them and not larger fish):
- Fish net
- 1 gallon bucket/container
- Small cup for carrying fish
- A whisk
- Clove Oil
- 1 measuring cup (that measures at least 1 cup)
Put the fish in the small cup. This is where he will sit while you are mixing the clove oil with water, and where you will mix clove oil with water later.