Ace is sick!

[magnum]

I'm unsure of what happened here. I got home from school and he seemed a little lethargic, but he still cam to the front when I went to the tank. A few hours later, I went to feed him and he was in the corner not moving and breathing heavily. As I watched he sank onto his betta hammock. He appeared to be dead and I watched for a little longer and he darted back to the surface for air, only to fall back down again. After this I put him in a cup floating inside the tank with a few cm's of water so he can breathe easier and some stress coat. I'm really unsure of what's wrong with him so anyy inf would be appreciated!

EDIT: He survived the night, but is still acting the same.

[Oldfishlady]

Complete and add the sticky info sheet found at the top of this section....The more detailed info the better we can help....Also add a pic...

Right now-if you haven't already-check the temp to ensure it is within range and make a 50% water only change-dosing the dechlorinator for the full volume-turn out the light-dim lit quiet location-hold food for now...Once we get more info we can go from that point.....