Hello, my betta Albus has some sort of a tear/hole in his tail, as can be seen in the following picture. He has also been behaving strangely, resting at the side of the tank with his body bent a bit, as in the picture. He lives in a 5 gallon tank that has some gravel and pebbles, a heater, and I feed him Betta Crisps once a day. He used to have a normal appetite and swam fine. He likes to hide behind the heater(which is shaped as a smooth spatula and is not sharp). Now, past few days, he became kind of lethargic, resting in the corner of the tank or behind the heater. I didn't notice anything on the tail then, but thought that I should do a 100% water change since a month passed since the last one. I took the Betta out of the tank and placed it into its old fishbowl. That's when I noticed the tear in his fin. I'm not sure if he had it already or if I somehow injured him while moving him. In any case, I left him in the bowl for another day, and his behavior is the same. He swims up for air then floats back down to the side of the bowl and rests with his bottom half lying down and his head sort of raised. He's also seems to have lost his appetite. I'm not sure what to do, since I don't know if this is fin rot. The rest of his fins look okay. Also, i use tap water and add dechlorinator. I have had Albus for about a year and four months now. Should I get the aquarium salt or something else or just let Albus try to heal on its own? Any help is appreciated.