This is what is left of my poor bettas tail. We have him in a 10 gallon tank and started with getting him just 1 live plant after reading bettas love them. We wanted to see how he liked it and he loved it so we bought him 3 more. He was so happy at first diving right into them, swimming all over and displaying his beautiful fins like never before. About 5 days later he disappeared and wouldn’t come out of his skull not even to eat. When I was able to get him out during a water change I noticed what you see in the picture, his tail is gone and is eating into his body. I quickly put fresh water in his 2 gallon tank and transferred him then hit the pet store where they gave me furan-2 and told me it should clear him up. Well I am into the 2nd round and he is still hanging at the bottom of the tank,not eating, he now has a blue sore like spot by his gill on the left side (I tried getting a pic but didn’t want to stress him out anymore). I don’t know what else to do. I am doing about 40 percent water changes daily and have him back in the 10 gallon, the air stone and/or filter was stressing him way too much in the 2 gallon - he doesn’t like all the motion in his tank. Please can someone help me save my baby?