my poor baby betta boy - standing on tail

Question
QUESTION: OK, I've had my betta, actually inherited from my daughter's friend who asked me to 'watch' him for a while.. two years ago. First, I must say five months ago we moved #he and I# from a house filled with people coming and going continually #my husband of 28 years decided to divorce me and my 20 yr old daughter and bf moved in w/ him# since then he seemed a little depressed. So I started 'talking' to him more and generally giving him more 'face time'. That seemed to perk him up. My room mate however, has a hard time remembering how to regulate his temperature in the aquarium that I have. She decided he needed it warmer because he seemed to be swimming more when she did. Well, it was 90...so I immediately decided to 'clean' the tank. Although I had the water START at the same temp...I didn't keep the heater that high and I let the water cool down.. But it seemed to cool way too fast the next thing I knew he was upside down. I used the net and brought him to the surface..he breathed and then went the the bottom and lay on his side. I kept bringing him up for air. Well, that was a week ago. He survived, BUT now he can't really seem to swim with his back half like his beautiful tail is too heavy and drags him down. Half the time he kind of stands on his tail in a vertical angle staring straight at the top of the water. His right fin works way faster than his left. It takes great effort to swim to the top and he will sit on top of his plant so that he doesn't have to swim so much to get to the surface for air. He DOES swim, but not much. I have to drop his food pellets right where he is or he doesn't seem to be able to see them. Can fish have strokes? Is it that or did she cook him? Is he being tormented by living this way? Should I euthanize him? Is he in pain? How do you euthanize a fish? Since becoming attached, I refuse to just flush him down the toilet..my whole point is in NOT causing suffering.
Sorry this is so long...

ANSWER: Jo,

 First thing i would do is drop the water level. She didn't cook him, but the ideal temperature is 82 degrees. What has happened is he went into shock. When the heat goes up and down as quick and as often as with him, his body cannot handle that. Also with the water at 90 degrees the oxygen level went way down. I would add an air stone to his tank to give him extra oxygen. Try to keep his temp at the same at all times. I think that if you lower the water level, and add an air stone, he might start to get better. They have what's called Betta hammock, I have a few. It is a large leaf that is suctioned to the side of the tank. The leaf can then be bent in any way you like. He might like that to keep him at the top of the water.  I think that when all this is done, he should start to get better. If temp needs to go up or down it is best to do it gradually. Sudden changes make them stress out and then go into shock and that can kill a Betta. Please, let me know how he is doing in the next day or 2. thank you.

---------- FOLLOW-UP ----------

QUESTION: I did all you suggested. He has slowly become more happy and alert. He swims more and he has started flaring at me again. His color around his face and gills is not as bright. He still cannot turn but one direction and still either lays on his side on the bottom, gets on top of 'hammock', or stands on his tail looking straight up. I've changed his water again being careful to maintain the temp. I put in StressCoat and Stresszyme at every change and I change it once a week. It's a small tank. So, now I'm wondering if along with the shock, I could have broken his back end trying to get him out with the net. I really know nothing about fish. All I know is that I've grown attached to the little fella, so I've learned what I can and I just want him to be happy and not suffering. He seems to be happy enough == though he can't stay afloat long enough to make a good bubble nest now because of this "thing" == other than the flaring, swimming, brightness of color, and activity - I don't know what else to look for to know if he's a happy camper but 'disabled'.

Answer
Jo,

Glad to hear he is doing a little better. I was also thinking maybe he has been injured. All we can do now is give him time to get better. They are very strong fish and hopefully in a week or so he will be almost as good as new. Continue doing what you are doing and make sure he can get to the top for air. If things don't get better in a week, or things get worse, let me know. Good luck on you baby betta boy.