This fish is a hybrid black zebra (D/g Z/+) close
examination will reveal the extra vertical band,
whilst the intesity of the black is not quite as dark
as a DD black.
One of the first
angelfish varieties to be developed was the Black
lace angelfish. Black lace angels look like normal silvers with the normal
vertical bands, but instead of the normal silver base colour they are dark grey.
There is some dispute as to who first discovered the "Dark" mutation
that causes this colouration, it seems quite possible that the mutation has
occured more than once. It is certainly well documented that gold marble fish
will occasionally produce a dark mutant.
Black lace results from a single dose (heterozygous) of the Dark gene. Black angels were first produced by mating two black lace fish to produce some double dose (Homozygous) Dark fish, these are sometimes refered to as DD Blacks. Very close examination of a DD will often reveal the vertical black bands but essentially a DD is solid black fish.
Unfortunately Black angels have a reputation for being weaker than many other varieties, one possible explanation being the need for a higher protein diet to allow the fish to produce the large amounts of melanin that give it its colour.
Many breeders now produce black angels by combining the Dark gene with a gold gene, this produces a fairly dark fish, but the black bands can be seen more easily, D/g blacks are often refered to as "hybrid blacks", and are generally considered hardier than DD blacks. A ghost (heterozygous for stripeless) angelfish, has no vertical banding, so a ghost hybrid black is very hard to distinguish visually from a DD black.
Black Blushing Angelfish also lack stripes, these are striking fish, often refered to as black velvets.