|Pomacanthus semicirculatus in an aquarium with blue background. Semicircle Angelfish. The Koran Angelfish, also referred to as the Semicircular Angelfish or Halfcircled Angelfish, is an extremely popular and hardy angelfish. As an adult, the body color is a yellow-green that bleeds from light to dark moving front to back along the body. Lighter areas are speckled-blue while darker areas have a more yellow-speckled appearance. The head is a plain yellow-green with sapphire-blue gill margins and eye rings. The fins are also outlined in sapphire blue. The juvenile is black with white and blue stripes.