Hi I'm new to fish keeping so please be kind. I've had my first Betta, Dexter, for about a month now. I cycled his tank before I got him etc. However he has fin rot, or so I think, his tail has gone all ragged and is getting shorter. He is kept in a 5gallon tank with heater 78℉ and a filter, he is now in a 1 gallon hospital tank, after daily water changes became time consuming, and I have added aquarium salt along with daily 100% changes but nothing seems to be improving. I thought it could be fin biting but I have never caught him doing it. He seems happy enough at the moment being the most curious fish I have ever seen, is there anything else I could do to help him? I can post photos if needed.