So last night was hectic. Long story short, a betta went into a new 2.5 gallon tank that had a heater that was overheating him, and a malfunctioning thermomiter. He started to display this behavior then, was removed from the water, and perked up after a few hours. I thought it was related to the heat.
Well, I put him back in. Sometime in the night (after I was up for several hours) he started again. This time he's much more energetic-- if he sees me moving he starts to swim around. But if he stops he goes compleatly belly up. He's in a QT cup, again. With just enough water to cover him and let him spread his fins comfortably.
I'm thinking now it must be a contaminant. Has anyone ever dealt with a similar issue?