I just noticed this a few days ago-it definitely wasn't there before that! It's a dark line that appears to be a section of his backbone! He acts 100% perfectly, and it's totally internal, there's no bump, or other external signs. You can still see it a little bit from the outside in these pictures, but normally you can only see it when the light is shining through him. I've never seen this before and it's really scaring me. Has anyone seen this, or anything similar to this at all before, in any kind of fish, fresh or salt? Does anyone have any educated ideas about it?
This annoying thing won't let me upload pics, even though they definitely fit-they're exactly the same
As every other thing I've uploaded on here! I'll try uploading them on a reply here