My hatchetfish has run into a bit of trouble... I was away for a couple days and when I came back, one of my fish's "wings" was drooping perpendicular to its body. It looks a little swollen, and I thought I saw a small, white stick-like thing poking from the bump. That's gone now, though. He can still swim just as before, but it looks painful... I think my golden killifish bit him or something. I saw him nip at one of my ottos today. Unfortunately I don't have a quarantine tank yet, but even if I did have one I wouldn't know what to do. Is there anything I can do to fix his fin?