So I have a halfmoon, Illy, who bites his fins when the water parameters in his 2.5 gallon tank are off. Obviously I've kept this to a minimum with keeping up with water changes. But I recently went on vacation for 7 days. I knew his fins would look bad when I got home. I did a 75% water change literally 20 mins before I left, and another 75% wc literally as soon as I walked in the door. And sure enough, his fins were ragged. So I put in aquarium salt and diluted melafix, as I've done in the past, and kept his water clean. So far there's been no fin rot, but now he's taken it to an extreme. It's become a habit now, and in the week since I've been back, he's shredded his fins even more. Obviously, when I see him do it, I stop him, but I mean, this is almost a constant thing now, as the picture shows. I don't have an extra 5g tank so I can't move him to something bigger. The only other fish I've ever had who bit his tail was a rosetail (I got him before I knew about their issues), and even he wasn't this bad. I've never seen anything like this before, and have no idea what to do. Water parameters as of yesterday: A: 0 Ni: 0 Na: 10 Temp: 80 2.5 gallon tank.