. I'm sorry you and your fish have to go through this.. It's might least favorite part of pet ownership as well but it sounds like he had a great life with you.
Oh yes I'm aware that they are fragile and pretty high maintenance. I think I'll stick with planted tanks for now.
Do you have any predatory fish who could do the job? I prefer swift deaths but I'd vote freezer over placing him out of the water. Suffocating would be much more stressful.
If you lower the PH and raise the temperature I think it could work. Many people are totally against mixing cold water and tropical fish but I have seen some experts find the right median.
That is quite interesting!
Love those angels!