I owned four betta fishes all in separate tanks. Two have 5 gallon tanks and the two lived in 2 gallon tanks. BEFORE YOU LECTURE ME OUT 2 GALLON TANKS. it's because two of my betta's hated big tanks, trust me I seen it. They would act depressed in 5 gallons and when my sister suggested switching to smaller tank I bought a 2.5 gallon tank that had filter, light and heater and they became more active in those.

One of my betta who lived in a 2.5 gallon tank died of old age.
and now I have another who seems to be suffering I have done everything for him treatments nothing is working. He is just dying. He has not eaten for about 2 weeks. He won't eat anything! All he does is lay on his side like he is dead float up get some air and fall back down. He was one of my healthiest and friendliest betta and it's killing me seeing him dying.

pets question and answers,www.5d2d.com

Can I put him out of his misery?
by trying this method
"put the fish in a plastic bag with enough water to make it comfortable, then, put the plastic bag in the freezer. As the water turns cold, the fish will drift off to sleep, and he will pass peacefully long before the water freezes. "

right now he is hunched over breathing slowly.

I am out of ideas he was bright orange, beautiful GIANT! but now he has gotten smaller and he is no longer bright orange.

Do clove oil and vodka. Add some clove oil to his water. The clove oil will work as a anesthetic. When he looks like he is not breathing/just laying there or floating put some vodka to make sure to dies.

The American Vetinary Medical Association has even said this is a inhumane way of doing it. Because they are not warm blooded and do not 'sleep' like warm blooded animals and humans. So they are awake the whole time until the heart freezes and stops the flow of blood. pets question and answers,www.5d2d.com

Your Betta was very beautiful by the way.

Good luck

I can't read a fish's mind so I don't know for sure which way is the least painful- but slowly freezing to death sure seems like it would hurt.

I use clove oil to euthanize fish.

A few drops in a small container of water will put it to sleep quickly, a few more drops will kill it.

Whats actually wrong with him? does he have a bubble tube? when ours unstuck off the glass and floated to the top our goldies would act dopey and constanly go up for air.
i personally wouldnt kill him, freezing him i would imagine is like putting you in a freezer till you freeze to death?
sure its not swimbladder? ask someone at your pet shop, they would know what they are talking about!

fill the container with water and him inside. put in few drops of clove oil. then pour in vodka to kill the fish.

i would just let him die on his own, i wouldn't kill it.