Unidentified spot on Dojo Loach
I recently purchased three golden dojo loaches. They came from a tank with a few other dojos and some fancy goldfish, all of which looked healthy. When I got them home, we noticed that one of them has a bright spot on his side, just behind his gill. It doesn't exactly look white, and it actually appears to be below the skin reflecting light. It has a distinct shape. I have attached a photo. I have had him in my quarantine tank for a few days. The spot has not changed in size or shape. He and the others I purchased with him all are acting fine. They seem healthy and completely normal.
My gut feeling is that the spot is just something distinctive about him, and nothing to worry about. However, I haven't seen anything like it on other loaches or in pictures. I would appreciate any advice/opinions as to whether I should be concerned, or treating him for anything.