His name is Tobias. He has a long black-and-brown thing hanging from the middle of him. The hanging thing isn't the same thickness in all parts. Tobias has been swimming slowly for a few days, but I didn't think anything of it for the first two and a half days or so because I had just transferred my fish to a new, bigger tank, and I didn't know the parameters in the new tank would be different from my old tank even though I used the same filter and media and the filter was built for the bigger tank's size and this caused all of them to swim slowly. But the other two fish starting swimming at close to a normal pace again yesterday and Tobias didn't. Now the other fish are swimming pretty normally and he's not. And he's having trouble swimming against the current of the air stone. I'll try to get a pic of him. I don't think I can get him medication tonight, but please tell me about any medication he needs and I'll get it tonight, if I can. What should I do to help him? Edit: now that I got a pic and I zoomed in on it, the hanging thing has some white, too. And the end of it broke off. Second edit: He's also been sometimes moving some or a lot, but staying in place. Shaking his fins or the main part of his body some or a lot, while not going from one part of the tank to another.