So last night my betta out of nowhere was in terrible shape. We had done nothing to the tank, no changes, and all of a sudden i checked him out when i got back from a meeting and he was twitching. every 30 seconds or so he'd have a head twitch, and he was no longer swimming around the tank, but just chillin in the corner.
Now, his fins seem to be deteriorating VERY rapidly (extremely stringy, id say he's lost about half of his finnage, and he has what looks like white fungus growing on the edge of his fins, around his eyes a little, and just a little on his side.
This happened so fast, so we isolated him in a one gallon tank, added a little bit of aquarium salt and some "betta fix remedy" which says it cures fungus and bacteria infections, fin rot, etc. He looks to be in terrible shape, doesn't even swim. He just floats until he needs to breathe.