The Lamarck's Angelfish (or Lamark Angelfish) is also called the Freckletail Lyretail Angelfish. They have the distinction among angelfish of being sexually dimorphic. Both male and female are a silvery-gray with horizontal black stripes from eye to caudal fin. The female's stripes are bolder with one extending into and covering the length of the caudal fin. In both, the long dorsal fin is black, although larger in the female, and the caudal fin is freckled with black.

More easily kept than some other angelfish, the Lamarck's Angelfish requires a well-maintained tank of at least 75 gallons. They may chase small, docile planktivores such as Anthias, Fairy Wrasses, Flasher Wrasses, and Fire Gobies but will usually ignore other fish, including other Angels. Only one male Lamarck's Angelfish should be kept per tank. Fish of the genus Genicanthus are the only zooplanktivores among the angelfish.

The diet should consist of Spirulina, marine algae, high-quality angelfish preparations, and mysis or frozen shrimp.