Hi, I've had my betta since 3 years ago when I rescued him from poor living conditions in a neighbor's house. His fins have always been droopy, but I've recently noticed they're a little stringy/ torn looking. I don't know much about fish keeping but I try to make sure I get the basic stuff for him. He's in a 5.5 gal tank, has a sponge filter with no strong current, no plastic plants just one big live plant, a smooth cave for hiding, and smooth pebbles on the tank floor. I do 30 % water changes every other week and he eats very well. Am I overlooking something? Is he just old? Any suggestions or answers are greatly appreciated.