There are currently three recognized species of wild angelfish, these are Pterophyllum altum, P. leopoldi and P. scalare. All three share a basic silver body with vertical black banding. Although P. altum are seen in the aquarium trade occasionally, P. leopoldi are only rarely imported. Most domestic angelfish are considered to belong to the third species P. scalare. However, many angelfish enthusiasts consider that there are several distinct species which are currently lumped together as P. scalare. It is certainly the case that there are several distinctly different wild populations currently classed as P. scalare.
The top two photos
show young "domestic" silver angels, sadly, although very attractive,
the red dorsals of these young fish will fade as they age. By contrast, the
two photos below show tank bred silver angels typical of fish found in the manacapuru
region. The distinctive red backs, sometimes referred to as red shoulders, are
not seen in most other wild types and only develop as the fish mature.
Silver angels usually have two body stripes, with a third through the eye and a fourth at the root of the tail, which the fish can "turn on" or "fade out" depending on mood. Notice that the tail stripe is much more prominent in the domestic fish compared to the "red backs". Notice also that the body is typically more rounded in domestic fish.