I got this from the internet though that is not where I learned about it.
"In my experience, clove oil is about the most humane method to euthanize a goldfish that is beyond help, which happens especially when they grow old and get sick. The active ingredient in the oil of cloves is "eugenol." But it is very important to use it correctly, because it does not dissolve easily in water. Get an empty glass jar from pickles or something like that. Fill it half way with tank water and drip in about 15 drops of clove oil. Shake it vigorously until the oil is dissolved and the solution is milky looking. Remove the sick fish from the home aquarium into a separate container and slowly add the eugenol mixture. Your old friend will be in fish heaven soon - a very merciful way to put your fish out of misery" Dr. Bill Brehm
I used a product purchased from AquaMeds. My instructions said that if you leave them in the water with oil of cloves for long enough (I left them in over night although they stopped moving shortly after being immersed and I used a healthy amount - 1 tsp - of the oil) they will die, not just sleep indefinitely. The instructions were very clear on this to assure if all you wanted was anesthesia not death you watched the fish carefully. I have used it both ways. To calm my koi for administering meds to ulcers and to kill them. I buried them in my garden. Great fertilizer. Or wrap them up and put them in the dumpster; water down the toilet is fine. Oil of cloves is a natural product and not a poison to humans; um might want to check on that last. Possible if ingested in sufficient quantities it could harm a person. But I know that I have used oil of cloves on my baby's gums (decades ago) when they were teething to cut the pain.
