Perhaps the most ambiguously described cichlids in the hobby today are Amphilophus labiatus and Amphilophus citrinellus. These two fish are practically identical under 2 inches, and even as young adults they can be difficult to distinguish. The confusion has become so prevalent that websites and even books mislabel these fish. In the following, I will give a few pointers that will at least give you an idea of which fish you may have.
Firstly, let us discuss common names to eliminate any ambiguity. A. labiatus is known as the Thick-lipped cichlid, and as the Nicaraguan cichlid, but most commonly it is called the Red Devil. A. citrinellus is known as the Midas cichlid. The popular belief among hobbyists is that the vast majority of Red Devils and Midas cichlids are hybrids (A.labiatus x A. citrinellus). Unless you received your fish from a reputable breeder/collector, you are to assume that either the Red Devil or Midas that you have is a hybrid. Even though these two species have been known to cross in captivity, the fact is that there is really no proof that the fish in circulation today are not pure labiatus or pure citrinellus. Of course, there is no proof that they are pure. Another reason the topic of hybrids is so prevalent.
This fish is a large growing cichlid reaching 12-14 inches in captivity. Its body is typically more stream-lined and lengthy in comparison to A. citrinellus. Its forehead has a slow slope, and although some specimens do grow nuchal humps, they are typically not as exaggerated as that of A. citrinellus. The snout/mouth of A. labiatus is also more narrow from side to side and longer compared to that of A. citrinellus and wild specimens often develop the thick lobed upper and lower lips. Its color range varies from orange and red, to pink. The color pattern also varies from solid to piebald. Juvenile specimens often have black spotting around the face and head, but this typically fades by the time they are sexually mature.
This is another large growing cichlid. It's size is comparable to that of its cousin though its characteristics differ in body shape. The body shape of the Midas is typically more robust and thick. Its body height is more developed than A. labiatus. Its forehead slope is more steep, and male specimens are capable of growing very large nuchal humps. As previously noted, the snout/mouth of A. citrinellus is more broad and stout than that of A. labiatus. Color ranges are vast. Red, orange, pink, white, and even a barred phase are common colorations. The patterns can vary as well from solid color phases to a piebald type pattern.
The following are pictures of A. labiatus (left) and A. citrinellus (right) all graciously provided by Jeff Rapps (http://www.tangledupincichlids.com)
The first set of pictures has just a few highlights.
The white circle represents the size and shape of the lips. Notice A. labiatus has very thick lips, and A. citrinellus does not. Although this is a very distinct characteristic represented by these photos, it must be noted that the lips become less and less defined through captive breeding.
The blue line is pointing out the body height of these fish. Notice that A. citrinellus has a very high body profile, and notice that it is very thick. Again, although this is very noticeable here, the height/thickness of any species does vary from fish to fish.