If I remember from my thread, Certain people raised issues about freezing, as there have been reports that people have done this and observed the fish. They have convulsed etc shortly before dying.
Would my Silver sharks I choose the clever method, Straight out of the tank onto a hard surface and BANG in one stroke. causing instant death.
As said at the end of the day do what you feel is best and what you feel you are capable of as the thing I was most worried about was pausing and therefore the fish suffering. Luckily or not I managed to complete the hole task in about 4secs from tank to death.
I didnt mean flushing dead fish was cruel, infact its a pretty sensible and clean way to "dispose" of a dead fish, this is what I did with mine.
I feel for you and your situation, but trust me things will get better either way. As the fish will no longer suffer or indeed recover (which I hope it does )
You will find the people on here pretty supporting whatever you decide to do
Freezing may or may not be the "best" method of choice, but it works for me. As I say, I have somewhat of a cold shoulder when it comes to my fish. I don't have attachments to them so it doesn't make me wonder what happens when I put them in a freezer. I don't do this often either, my last fish having died in 2002.
Have you been feeding floating food? Maybe it has gas in it's belly. Or it has an internal infection.
First stop feeding floating pellets. Be sure to soak them in tank water before you give them to the fish.
Next, try adding some Epsom salts to the tank, it is a laxative, maybe it can pass some of the problem. Be sure to vac the tank well to remove any infected feces that come out, don't want that to be shared among the fish.
Then see if there are any medications that you can get that treat internal bacterial infections. Medicated food would go right to the problem if you can find any that address bacterial problems. Ask around, maybe someone here knows about medications.
But, first, try to see if it is a mechanical problem -- bubbles in the gut.
If she's still eating OK and not being picked on, then I'd leave her alone. She may recover, or may not, but if you put her down she'll definately not.
If its a danio or a small tetra or something common like that I euthanise it. If Its a synodontis or the BP, or the gar or sevrum, or the rapheal, or the mudskipper or something that isn't just a tank filler, I do what I can to save the fish tell the end.
I think what your fish has is probably swim bladder. I am having a similar situation with my weather loach. Here is a link to the discussion on the swim bladder. Maybe it will help. By the way. I think that the freezer method is cruel if you dont sedate the fish first. Just think, how would you like to be put into a freezer til you died. Doesnt seem like a very plesant death to me. I am not judging those of you who do this, but it isnt the option for me. I think that just bashing the fish in one death hit is the best option. But, you have to make sure you dont miss. Or you could just feed it to the cat. j/k.