Sick or Bored Betta?

[cjrom1022]

I’ve had my elephant ear betta for about 2 months now. he’s always been kind of sluggish, but recently i’ve noticed he lays on the bottom for most of the day, and occasionally gets up to move to a new spot. His color also faded a lot, and his tail fin has become damaged. At first i assumed it was a bacterial infection so I treated with furan-2. it seemed to help slightly, but he still doesn’t move much. He’s in a 10gal tank and all water parameters are fine. The filter has been running for over a year, so it’s definitely cyclical. There’s not many decorations in the tank, just 2 live plants (java fern) and some rocks. I read that when bettas are bored they nip at their own tail, or if they’re in a big tank they’ll do it too. any ideas of what’s going on? here’s a picture of his full body and what his tail+faded color looks like (water is yellow from furan-2)