The animal on the cover of Programming WCF Services is an angelfish. Angelfish are found in tropical and subtropical reefs around the world; there are at least 86 different species. The average size of an angelfish is about 7 to 12 inches (20 to 30cm), but their size varies greatly, as does their coloring, which changes with maturity.
Their diet consists of algae, worms, and various shellfish and small sea creatures. A spine on the gill cover differentiates the angelfish from the also colorful butterfly fish. Depending on the species, angelfish have different mating habits. Some mate for life in territorial pairs, while others create harems of female fish with one dominant male. All angelfish are protogynous hermaphrodites, which means that if the dominant male were to die or leave the group, a female would morph into a male for mating purposes.
In some countries angelfish are used for food, but mostly they are caught for aquariums.
Rare species of angelfish can range in price from hundreds to thousands of dollars. In addition to collectors,angelfish are threatened by reef destruction and continual environmental degradation.