GobyMaster11276
Fish Crazy
It might be difficult to tell through photos, but there is a fuzzy growth (what I assumed to be fungus) along the dorsal and tail fins, situated around the edges. If you look at the parts where the fin seems irregularly shaped, you should be able to see it, particularly on the top of the tail.That fish appears to be in a typical "c" shape. This generally indicates poison. Could be ammonia, nitrate, or some other toxin in the system. I do not see any fungus. It is rare that fish in this condition recover. In my several years of disease assistance on goldfish forums, I haven't seen even one C shaped fish recover. That's how rare it is. There is not much you can do for him beyond keeping his water clean. Random medications thrown at him are unlikely to help.
I honestly would euthanize any fish I had that ended up in this condition, but that's always a personal choice made by the owner and owner alone.
It might be low odds of a recovery but, given that he has kept fighting for the last week, I feel it best that I exhaust my options before euthanasia.