I actually find this subject really interesting - interesting enough to spend the last couple of hours researching it. As smb said, for years, I've heard that putting a fish into the freezer in water is the preferred method for most hobbyists. When I first joined this forum, I read Dragonslair's pinned article about euthanasia, and was curious about his statement that freezing them in this way causes immense pain and stress. Furthermore, I was somewhat disheartened by the advice given there, because I'm POSITIVE that I'm not the only dedicated fish owner who would NEVER have the heart to decapitate or bludgeon my fish to death. I couldn't even bring myself to decapitate a live caterpillar, let alone one of my beloved fish. I'm not saying it's not the best way to euthanize, just not reasonable for a lot of people.
This is what I learned in my research. Firstly, as Dragonslair stated at the beginning of his pinned article, his advice is from the perspective of an ichthyologist. Anaesthetic in lethal doses is the most commonly used method, followed by decapitation and pithing (stabbing the brain). However, no less than three of the sites/books I've just read stated that the anaesthetic method was not reasonable for the hobbyist, as the only approved drug for the purpose of euthanizing fish is not available to the public (*note* I don't know if that is in the US or the UK, assuming it was the U.S. ), and the decapitation method was recommended AGAINST for the average hobbyist, as it is possible, and in some cases likely, that it could be done incorrectly. Furthermore, it was recognized that many hobbyists would not be comfortable with doing so. The other method discussed was putting the fish into a plastic bag and smashing them against a hard surface. Again - not for the weak of heart/stomach.
Some sources recommend putting alka seltzer tablets into a cup/bowl of tank water with the fish. They suffocate from the CO2. Another frequently recommended method is to put the fish into a cup of grain alcohol (vodka, gin, tequila) or alcohol mixed with tank water. I don't think I could do either of those things.
Almost every single source I found (save for one) recommended the freezer method. The thing is, you don't put a guppy in a teaspoon of water in the freezer, or an oscar in 2 cups of water. You'd put a guppy in at least a litre of water and an oscar in at least a gallon (preferably two). The smaller the container, the faster it will freeze. If the container is large enough, the temperature will drop slowly enough that the fish's metabolism slowly shuts down until they're permanently sleeping, so to speak. I'm not a fish who's ever been frozen to death, so I can't say for sure if it works, but it sounds reasonable to me.
Here's the thing. Obviously, decapitation/pithing is faster, but as I've already stated, there is a ZERO percent chance that I could bring myself to do such a thing. That decided, what is better, to leave the fish in the tank to suffer for perhaps days or weeks, or to put it into the freezer where it MAY suffer for the next half hour or so, but is definitely dead at the end of that time, with no Jeffrey Dahmer-esque nightmares for the fish owner?
As always, just my two cents worth
One of my baby (4 months old) Oscars has developed a horrific fungal infection which has not responded to any treatments has developed a secondary infection of the swim bladder and is now dying, and appears to be suffering badly. I know that the only thing i can do to reduce his suffering is to put him to sleep. But I've never done this before. Can anybody please give me some advice as to how i should do this in the kindest way possible?
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