Treating finrot

[Aquaria]

Any way to treat said disease in dt guy at LFS told me to buy melafix or w/e but I'm not using that stuff after what I read he's a 6 line and I really don't wanna try to catch him.. I was reading about putting antibiotics in the food sounds better also I got him like this he was being picked on. he wasn't eating when I got him 2 days ago and he was eating like a pig today.