The red 'spot' looks a little like a small nick - any chance he has caught himself on a sharp ornament, or been nipped by accident by a tank mate (or, amazingly, that he might have nipped himself)? Keeping the water cool and clear should sort that out if it is.
A good way to see if it is a harmless pigmented spot - an iridophore - is to shine a torch at it. If it shines back white/silvery/yellowy then it is an iridophore. My Golden has tons down her tail, with a few on her 'shoulders' and head. If it's fluffy, cottony or comes off when touched it is either fungus or skin shedding, but to be honest, it sounds like an iridophore in my opinion.
Also, I don't want to be rude but he looks a wee bit skinny. Is he on worms? Or is he a picky so and so like my male and only eats when he feels like it? (My boy is slimmer than my female, as males tend to be, but he sometimes downright refuses to eat).
on body/gills. No others have anything similar. Thoughts?
