I did a 100% water change today complete with water conditioner, acclimated fish, put fish in new tank, fish was happy, he had an early dinner and I went out.
I came home and sat down next to my tank to say hi & check the water temperature and I noticed a dark spot on the side of him. It could have been there all along and I just overlooked it, or it just appeared. I don't really know. I do have pictures, but I'll explain a little bit. They are on his left side behind his fin. However, he does have a dark (almost black) head, so I don't know if this is just his color, or if he somehow got a bruise. Is that even possible? He is swimming fine, begging for food, no labored breathing, no peculiar behavior.
Close up, kinda blurry but you can see the dark spot.
Far away, but clearer. He is bringing out his color as he was a Walmart fish and spend God only knows how long he was in his little cup without a proper water change. Any suggestions?