Help! Lethargic betta

[glassonion]

I recently moved Heloi and his tank mates (3 neon tetras and 2 juli corydoras) from a 10gal tank to a 29gal tank. My tank now houses
Heloi (betta)
10 neon tetras
6 zebra danios
5 juli corydoras

everyone has been happy and active since last monday when the new fish were purchased

today i woke up and couldn't find Heloi. He was hiding in behind the java moss on the bottom of the tank and his body was sort of at a weird angle, so i went to scoop him up with a net and he moved really fast and shot up to the top of the tank and then went back down and hid in a tunnel for about 15 minutes. i was feeding everyone as this happened and he was not interested in the food whatsoever, which is very not like him!!
as i type this, he's swimming around now but still not eating (i just dropped in some more food and nothing)
and now hes hiding again in a tunnel

what's wrong? i've had him for over a year and he's never been like this

[glassonion]

he's swimming around again now
which makes me feel a bit better
i just want him to eat

[glassonion]

[glassonion]

anyone???! :(
i moved him to an empty 10gal tank now
he has kind of like fuzz on him now too :(

[MyRainbowBettaFish]

could be fungus if it is fuzzy and white

[jriley]

Quick! If he has fuzzy stuff on him its time to check the Stickies up at the top of this page. It'll give you a guide to how to treat him. Good luck!

[glassonion]

He was floating on his side barely breathing so I went out and purchased API Bettafix
I couldn't narrow down what was wrong with him... the only thing from the stickied threads that sounded like him was Body Slime Infection and none of the medications at Petsmart mentioned anything like that
I came home and put the appropriate amount into his tank and went upstairs for an hour and when I came back down he had passed away
:(
RIP Heloi