Any advice for combatting fin rot in a betta fish?

I have a reddish-orange betta fish that used to have long, flowing fins. I just noticed that the fins are not so long and flowing any more. I googled “fin rot” and read that you have to change the water in the tank, and wash all of the decorations in hot water

I feed him blood worms (freeze dried) and I only feed him like every 3 days, because I read you should not overfeed them. He’s in a one gallon tank with a filter. I got this fish about six months ago.

Do you have any advice for combating fin rot in betta fish? Do the fins grow back?