Ami brought my attention to this method some months back, Thanks Ami and feel it is the kindest and gentlest way to put fish to sleep

http://www.wisegeek.com/what-is-the-m ... y-to-euthanize-a-fish.htm

How very sombre...
I guess this is for illness primarily?

Yes as a last resort if the fish is very ill

Definition:
Euthanasia (Greek, "good death") is the practice of killing a person or animal, in a painless or minimally painful way, for merciful reasons, usually to end their suffering. This article discusses euthanasia in humans; a separate article covers animal euthanasia.
en.wikipedia.org/wiki/Euthanize

ive just read this out of curiosity, if the fish is ill and carnt be cured its probably for the best, but it made me cry just the thought of it:(

I think im going to have to do this to my Ryukin, the poor little guy has a very severe case of swimbladder, i have tried absolutely everything and nothing seems to be working, he is floating on his side at the surface unable to eat unless i feed him by hand (which is what i have been doing) upsets me to look at him at the moment so think this may be the only option i have now.

There is an alternative method for euthanasia of fish that i picked up whilst working at the london aquarium. If a fish is that ill that it will not survive or in some cases if the disease does not respond to treatment and is highly infectious it may have to be culled to save suffering. Simply place the fish in a container large enough to support the fish for a couple of hours and place this container in the freezer. as the water cools the fishes central nervous system begins to slow down and the fishes enters a hibernation like sleep state. The fish, then unconcious then dies in its hibernation like state with minimal stress. This is merely an alternative method for times when clove oil may not be availiable.

Unfortunately its not really true. Although the fish will die the panic and pain caused by slowly freezing it to death is now understood to be quite severe and not humane at all.

A fish can actually feel the ice crystals forming within its body, they tear through muscle tissue causing much pain and suffering. Many studies have shown fish to have well developed nervous systems-and they show clear physiological response to pain in experimental trials.
Clove oil and vodka.....fish owners should keep them in just incase, but if not, it won't take you any longer to pop to the shop and pick some up than it would to freeze your buddy to death in your ice box. Please don't do it.

I'm sure none of us on here would want to be frozen to death . . . Why should we do that to any animal - not just a fish?! I, for one would rather buy the clove oil . . . And we usually have vodka in the house anyway