Yes, using dechlorinator. Bettas don't require half, they are just as sensitive to chlorine and heavy metals as other fish, just often times they are put in very small bowls.

Only meds I've been using have just been the epsom salt and natural tannins, but he has been in straight clean water since he got over his illness. Trying to use natural cures, I know too well how much medicine can actually damage a fish(Bettafix! Ugh! It has caused too many deaths on the betta forum I frequent)

So he's still getting just the clean water. I do think I need to start him in AQ salt soon as the fin rot is spreading horrifyingly fast. By this afternoon his dorsal was almost completely eaten away by the rot. Very scary, I've never seen it move this fast. Possibly a fungal fin rot, which is going to be more tricky to treat.