I got my new (and only) betta, Otto less than a week ago from Walmart. He's in a 3 gallon tank with a heater (temp is 76-78 F) and a Whisper 1-3i filter. Last night I was doing some research and I think my boy has some fin rot. The edge of his tail is clear with a dark edge and is a bit ragged looking. The edges of his pectoral fin are clear as well but with no dark or ragged edges. I did a 100% water change last night and added a tablespoon of aquarium salt for each gallon. He seems to be acting/swimming normal. I took some pictures of him in his water change cup last night, so if you all could tell me if it's fin rot that would be great. If it is fin rot how often/how much should I change his water? Should I keep adding salt? Is there anything else I should do for him?