euthanasia for Beta

Question
I have a Beta I purchased April 2005 so considering the average age when purchased he is getting up in years.  He has been a happy bubble blowing little guy. I've had him in a  30" diameter glass sphere.  I have religiously siphoned the water low every 4 days and completely changed the water and cleaned the bowl and rocks once a month and kept the small plant bulbs that grow for Betas in there.  Now he has become pretty much completely blind.  He lunged for food but rarely got it and would settle on the bottom of the bowl mostly on his side and not move around much anymore.  I decided to put him in a small bowl, 15" diameter so he wouldn't have to lunge so far and to keep the pellets grouped and put lots in to make his chances better. This has helped and he does get at least one pellet everyday.  and doesn't lie on his side much anymore, in fact, he uses the little plant to help hold him up.  Then I take out what he hasn't eaten to keep the bowl clean. I also bought larger sized pellets that are orange.  He has always had a little lamp over his bowl which gives light and keeps the water temperature warm.  When he cannot eat at all I could not abide his slowly starving to death so I want to know if there is something I could sprinkle over the water that would pass through his gills that would cause euthanasia quickly? Is there such a thing?  Any other suggestions?  He's such a nice little guy.   Thank you for your response.

Answer
You're right, he is getting up there in years.

This could be the last little time he has left. It is your choice really, there are no fish euthinasia laws.
You decide to let him die or pull the plug.

Now, for your question.

There are many ways of euthinasia. I find only two too be truly quick.

1) Clove oil and vodka. Put the fish in 100% clove oil. Its like anesthetic, the fall asleep. Then you can pour vodka in, or boiling water. They won't feel a thing. Go to sleep and not wake up.

2) Cutting off their heads. I don't know anyone that has ever wanted to try this method, for obvious reasons. But I feel inclined to mention it. You can take a knife and severe the spine at the baswe of the head, or take the head right off. It's definitely quick if you do it right, but not the happiest thing to do.

-Nick