My betta had a fake coral in it's tank, and he ripped his fins on it. So I took the coral out, kept the water clean, changed the water regulary with the conditioner, and temperature is always on 27 degrees celsius (80f). He is in a 8L tank (2 gallon), with no filter.
It has been more than a month now, and I haven't seen any difference at all. Luckly he has not developed any rot yet (I think). I've used a tiny amount of aquarium salt to see it it helps, but nothing. I've also tried to using almond leaves (left it inside the tank for about a week), but that didn't do anything either. I don't know what else to do to.
Here are some pictures.