You're welcome. I hope this has helped.
For my fish, to make the whole experience as stress free as possible, I used a clear cuplike container to slowly dip my fish out. Basically let him swim into it.
I sat the container on my kitchen counter, and I even had a piece of short sword plant in there with him (guppy), and while still in the container I diluted 1 drop of clove oil in about 4 oz. of tank water, in a turkey baster actually, shaking vigorously, and slowly dripped it into the container, which held about 8 to 12 oz.
He swam around peacefully and after about 5 or 10 minutes started swimming slower. He eventually settled down on the bottom of the container and was breathing normally but lay on his side.
I know he was asleep, just like when you are unconscious during surgery. I mixed up the fatal does in another 6 oz or so, and added a drop at a time over the next 5 or 10 minutes.
During this he was still, but for his breathing, and his breathing became more shallow until it stopped completely. I left him in this for about 30 minutes and then put him in the freezer.
The reason I've given you the details of this procedure, as I had to perform it, is that some on this forum think that a severe blow to the head of the fish is quicker and more humane.
Or plunging a knife into him behind his head, severing the spine.
To me, though, the act of holding him or laying him on a flat surface seems traumatic and stressful. Also, I am afraid I wouldn't successfully deliver a fatal blow, and would have to make one or more attempts, which would be horrible for him and for me.
I wish you the best, friend, and want you to know I am truly sorry for this sad loss you have suffered.