I've had my betta Scully for about 10 months. He's in a 2.5-gallon tank with a filter. Recently over the past month, I've noticed his lower fins have gradually been becoming translucent. I have no idea why.
When I started noticing this, I replaced the filter more frequently, changed his water at least once a week (half the tank with treated water of course), and removed a new object I had recently added in case that was causing him stress and to give him more space. I feed him pellets and/or dried worms twice a day. During the most recent water change I scrubbed everything (no soap) and rinsed the sand, in case there was bacteria living in it.
Can anyone look at the photo and tell me what this is? I'm not sure if it's fin rot, old age, or what? I've Googled ad nauseum and can't find another betta that shows the same symptoms.
I have this Betta Revive medication
, but haven't used it yet because I'd rather not give him unnecessary drugs if he doesn't need it.
Thanks for your help!!