Question
Hi, I have a goldfish in my pond that is swimming crooked.
It almost looks like he's bent in half.  I noticed this on Sunday and added salt to the pond to see if it would help.  I also put melafix in the pond today.  I took the fish out to examine him in a bucket and noticed that he has a large legion (like he injured himself) on his side.  Could this sore cause him to swim like this.  He is still eating.  Thank you.

Answer
Unfortunately, this problem is pretty common.  From my web site:

"Here are some reasons a fish may develop a bent spine.

If born that way, the fish may have a genetic abnormality.

If born that way, the fish may have incurred a developmental problem while growing inside the egg. This could be related to diseases, temperature, injury, etc.

If the fish was shocked via a faulty heater, pump, etc. or via lighting (striking a pond or surging through a house), this can result in a bent spine.

A severe injury can bend the spine. Normally though if broken, the fish would die right away.

Fish tuberculosis sometimes results in a gradual development of the curvature of the spine. I have seen this often in zebra danios but also in a golden orfe and a few other species. A fish with this condition (fish tuberculosis with a bent spine) is often also anorexic. See this section for more on fish tuberculosis.

Certain vitamin deficiences can result in spine curvature.

It seems that many fish nearing the ends of their lives get bent spines which usually match one of the above problems but sometimes do not."

The sore on the side sounds like it could be a physical injury which may have also injured the spine.  I worry that the lesion could be a fish tuberculosis tumor.  Fish tuberculosis also can cause curvature of the spine. My section on that is at http://www.fishpondinfo.com/health2.htm#bacteria
I hope that's not it.

The salt sometimes helps with problems but there may not be much that you can do.  Antibiotics can help with the lesion to some extent.  I wish I had better news.  Good luck with the poor guy!  He may live like that for quite a while.