I just got my male elephant betta 5 or so days ago. He was absolutely great the first 2 days; he swam around a great deal and his fins were absolutely fine. For the past 2 days, he has seemed a lot more mellow; lying on the plants a lot more, sitting near the heater in the back.
Well, he's come out into the open now at a time I'm here; The size of his fins are now literally less then half the size then what they were when I first got him. The fins are more wide at the root, and slowly get smaller. He's having trouble swimming now (it's clearly not a buoyancy issues, however). This took a max of 2 days to happen.
He lives in a 10 gallon tank; 79F as a current temperature, his filter is currently off, tank has silk plants and sand as a substrate.
Bought him at a chain pet store.