My betta has recently started to develop bits of white on his fins. They started near the edges and now patches have formed on the surface of the fin. The patches kinda look like a mould or fungus: i know it's not a mould, but it's the best way to describe it. The patches aren't on his body or head, just fins, which don't seem to be changing shape/colour.
His appetite hasn't changed and neither has his colour.
Just a bit of extra info: there has been a filter in the tank but i adjusted it to be less powerful, but it doesn't seem to be as effective. I've changed it back to make to make it more powerful, so hopefully that'll help.
Any ideas what this is and what to do about that? Thanks!