Neon Tetra acting strange? Bobbing up and down?

Hi, I have had a neon tetra for about 4-5 days now & he was fine the first few days. Yesterday I found him swimming in the back of my fish tank low then I realized he was acting strangely, he started doing curve jumps and swimming oddly then he would flip over and float as if he died, but then he would regain consciousness and swim normal. Now it was doing that for about an hour (I managed to record with my iphone - the link to the youtube video down below).

now I'm not sure if this is neon tetra disease because I did not witness previous stages such as loss of appetite and colour changing. However he has yet to eat any food since I found him doing this yesterday. For precaution reasons and in case he died over night (fish would nibble on him then get infected) I transported him from my 10 gallon fish tank to my 1.5 gallon fish tank (I only filled the water half way). He has been there all day today and most of yesterday but he is not eating the food I provide to him, also he is still doing those curvy moves but he has stopped. Today all he has been doing is bobbing up and down with his face up. It looks like he is in a lot of pain. Can someone tell me what is going on and what I should do?

I can see that it is suffering and I would like to put it out of its misery (since neon tetra disease has no cure), but I refuse to take him out of the tank and have him suffocate to death. I also need the body to return to the pets mart to get it exchanged since I bought him a few days ago. I was really hoping id find him dead by this morning to end its suffering but all day today he has been bobbing up and down, it is really sad.

My tank: 10 gallons, it has fish, shrimp, and a moss ball.

Here is the youtube video that I recorded:

Tetras need fresh water not saltwater if you didn't already know. I had a neon tetra and they must swim in schools so you have to get him at least one other neon tetra or he will go crazy trying to find his school of fish. Try getting him a friend to school with, if this doesn't work look for fish medicine drops in pet smart they usually have some. Erratic swimming could b due to him looking for his school of fish

An easy and quick way to humanely euthanize him is to get some clove oil, and mix 10 drops per cup of water, and place him in it until he stops breathing. Also, when you return the body, bring a sample of your tank water, as they will think it's the water that killed it, and do a test to prove it wasn't them, and they will try to put the blame on you.xP

Neons are very sensitive, the need a well cycled, well established tank of 20+ gallons, they need to be acclimated very carefully before releasing them to the tank. If you didn't spend at least 90 minutes acclimating them, you didn't spend long enough. Neons like to be in large schools or they get stressed. Please do not get another one, you do not have room for a school of 6-8 neons, which is a bare minimum sized school.

Many people believe that cold blooded animals can't feel a slow transition from warm to cold. It is widely believed that they start to get sleepy, and after a point, they will never wake up. If you put him in a cup or bag of tank water, and put it in the freezer, he should doze off without pain and die in his sleep.

A hard fast blow will end his suffering instantly. You could keep some clove oil around to use in the future.

I'm sorry that you may have to do this, It happens in the best well kept tanks, but please be more care-full about what type of fish you buy and their needs.