Some time ago a member of the livebearer mailing list (ALA) noted that Aquarium Products company now sells a product called Euthanase, to put a seriously injured or badly torn up fish to sleep. They suggest that if medication or surgery can not help a fish in great pain or with an incurable and contagious dangerous disease (such as fish TB, probably dropsy), then the fish can be put in a small container and the stuff given in a two step procedure. The first dose is supped to put the fish to sleep. The second is supposed to stop its bodily functions. They offer a table of what does to give to what quantity of water (in a small container).

The manufacturers are very clear about keeping the product out of the reach of little kids. (I'm not sure that can be done with some resourceful climbers.) First aid instructions are given for cases where Euthanase is ingested, or splashed in the eyes or on the skin.

I'm assuming that these things are also printed on the squirt bottle, hopefully so everyone can read them.

A Material Data Safety Sheet (downloadable at the site mentioned below) suggests that the active ingredient is a Plant Oil Extract. It notes that a user should was with soap and water after using. I would guess a disposable container (like a drink cup from a fast food place) might be the best place to administer the treatment, after which the fish and cup are disposed of in the garbage.

They are suggesting that in most cases one would not get any of that material on one's self. It is administered in drops from a small dropper bottle. So many drops per ounce of water are charted. The ounces are also equated with cut, pint, quart and gallon containers. (I'd sure use a cup or even a half cup if I could.) Drop equivalencies for 1/6 , 1/4 , 1/2 teaspoons and two teaspoons of the material are used.

If a fish is best put down, this may be the way to go, especially if a person does not consider the other methods discussed as appropriate or possible.