I put my fish to sleep and woke him up again.
I got together all the necessary items after reading several sets of instructions online. Bought pure clove oil at a health food store. I put a gallon of fresh conditioned water in my small bucket, and a small amount of water in plastic box. Put a tee fitting on two pieces of airline and ran a small airstone in each container with the pump. Put a small amount of water into a plastic baggie and added just one drop of clove oil. Shook it to dissipate the oil (it has a very strong scent!) Caught the fish- that was easier than I expected. I gave him a flake of food, held a clear plastic cup at the ready and just scooped him up from the surface when he was focused on eating. Put him in the plastic box of water. Added a small amount of oil-infused water. Watched the fish for ten minutes.
Nothing happened. I added another portion of water with clove oil. Still nothing. He just cruised in circles testing the boundaries of the box. I put another drop of clove oil into the baggie, shook it again, dosed his water again. This time he reacted- jerked around and dashed at the corners trying to escape the container. Started moving sluggishly and finally lay still near the bottom but when I put my hand in to hold him close to the side of the container he thrashed around again. I dosed another amount of clove oil water, waited another ten minutes. Again he reacted when the oiled water went into the container, gasped around at the surface, jerked about the corners and spit out the flake of food he'd eaten. People say this is not stressful for the fish, they just go to sleep but he sure looked alarmed to me. But of course when he finally fell asleep I was able to do a close inspection without further distressing him.
It was kind of freaky to see him finally lie completely still, fins held stiffly, his body drifting a bit with the current from the airstone. When I moved him with my hand he twitched a bit and I saw his gills moving, so knew he wasn't dead. (Clove oil is used to euthanize fish). I was able to hold him close to the side of the plastic container for a look with the loop and a photograph.
And he started acting stressed, raising his head in jerks so I quickly put him back in the container, then moved him to the fresh water in the bucket. It took him a long time to come around, which was alarming. I don't know if I'd kept him under too long- and I worried for a while that I'd given him brain damage from oxygen deprivation! For quarter of an hour he just drifted around with the current, belly up as if dead. Then he was able to right himself and moved around slowly against the bucket side, just moving one pectoral fin that was free in the water, the other one still. Tail down, head barely up- I kept moving the airstone near him to assist his breathing. I added another half gallon fresh water to the bucket. After a long while he started using all his fins, but still swam erratically, looked groggy. It was almost two hours before he was back to normal and I felt comfortable returning him to the tank.
Phew. So now I know how to anesthetize a fish, but it was kind of nerve-wracking. And seeing how he jerked around distressed when the clove oil was added to his water, I'm not so sure that using that is the most painless form of euthanasia. Knocking a fish on the head or stunning them with ice water would seem quicker. But I'm glad I have it on hand and after putting my photo and description of what I saw under the microscope on the forums, I got some useful feedback that helped me to diagnose- see following post.