I doubt the tangled up in cichlids site will do much to help out here. I have personally never seen a red devil with lips like that. Eventually, even wild caught specimen's lips shrink into more of a 'normal' look.
I have done lots of research on this, as these are pretty much 2 of my fav fish, and I am trying to breed a true strain of them. This is how I differentiate them, besides 'eye-balling' them.
1. Pics (especially red devil x midas hybrid) are a bit fuzzy, but bear with me.
On the red devil, when the fish is head on (not quite in this photo, but close), and in a head down position, the snout should come to a point, or 'V' shape. This does NOT guarantee pure 'Red Devil' (labiatus), but at the very least, you are guaranteed NOT a pure Midas (citrenellus).
On the Midas, you can clearly see a more 'U' shaped mouth. It never comes to a point. I have yet to see pure midas strains have a 'V' shaped mouth, though admittedly I can't say it is 100% accurate. I can't even give you a rough figure, but I do believe it is by far the most reliable method overall, next to genetics.
Immature midas also look rather like a red devil on steroids. Ignore the head. Hormone induced hybrids between the two from the east will have heads growing prematurely, but look at the general build of the fish. A young midas will look more like a bull mastiff and a red devil will look more like a great dane.
You keep looking at them enough, and abide by the rules above, and I would bet that after a while, you will be able to distinguish them with a high percentage of success. I know I can't do it 100%, but I would bet I am close.
I am from Canada, so I don't really know where you can obtain some.
