Thanks for filling out the sticky. You obviously take good care of your guy.
My next question is how many pellets do you feed at a time? I'm concerned that your guy may be constipated. If he is, that can affect his swimbladder and cause him to float at the top like he's doing now.
I suggest you put your guy in a small barebottom container (the cup he came in from the pet store, if you bought him, is good or anything of like size). In a 1g container, mix 1 tsp of epsom salts with dechlorinated water. Pour that in his barebottom QT container and put him in. You can float this container in his regular tank so he stays warm. You'll want to change the water every day and continue this for 10 days. Keep an eye out for poos.
I hope he gets better soon.
Oh, I always forget. Put some plastic food wrap over the top of his container and poke a few holes in it. This will keep the humidity in and also keep him from jumping out. Always forget that part.