Well, after a water change the bulge started residing and today [feb 05] she looks like she's back to normal.
Still don't know what it was, but whatever it was it seems to be over. biggrin
This week I've noticed a slight bulge on the right side of one of my goldfish.
Could someone help me diagnose?
Here's a picture:

I've always believed that goldfish can change color trough out their life, and my gold fish has been losing a lot of her color in the past two months, but now I'm worried that it may be related to the bulge at her side.
picture:

Also, I've always been meaning to ask, can a bend in the tail such as the goldfish at the bottom has, cause the fish problems?
She is the skinniest of the three.