Looks like a 'sp. Coatzacoalcos' or 'zonatus' mainly based on the bar running from the eye to the gill plate. Also, the solid black line running the full length of the body and the blueish overall tone. IME, 'hartwegi' has more red on it and doesn't have the dark features of the 'sp. Coatzacoalcos' or 'zonatus'. Here's a pic of 'sp. Coatzacoalcos' and 'hartwegi' for comparison.
i had a fenny that looked very close to this but with alot of pink on its head so im thinking this is more like a zonatus....i hate vieja id's! anyways nice looking fish
Looks like zonatus to me. Seems to have a bluer hue to it where young Coatzacoalcos I've seen were redder with larger spots along the flank above the lateral line. Maybe it's just the lighting.