(Pygoplites diacanthus) is a beautiful marine fish species that is found in the tropical waters of the Indian and Pacific Oceans, including the Red Sea. This fish belongs to the Pomacanthidae family, which includes other species of angelfish. The Royal Angelfish is known for its striking coloration and distinctive body shape, which make it a popular choice for marine aquarium enthusiasts.

The Royal Angelfish has a compressed oval-shaped body, and it can grow up to 30 cm in length. The fish has a blue-green body with a yellow tail and a broad vertical white stripe that runs from the forehead to the base of the pectoral fins. The fish also has a dark blue-black ring around the eyes and a bright orange-yellow spot just above the pectoral fins. The fins of the Royal Angelfish are also blue-green, and they have white margins.

The Royal Angelfish is a solitary fish that prefers to live in coral reefs and lagoons. It is often seen swimming near caves, crevices, and overhangs, where it can find shelter and protection. The fish feeds on a diet of algae, sponges, and other small invertebrates, which it grazes on throughout the day.

In terms of social behavior, the Royal Angelfish is not known to be aggressive towards other fish species, but it can be territorial towards other angelfish. It is best kept in a large aquarium with plenty of hiding places and ample swimming space. The water temperature should be maintained at around 25-28°C, and the pH level should be between 8.0-8.4.

The Royal Angelfish is a beautiful fish that requires a specific set of conditions to thrive in captivity. It is important to provide the fish with a healthy and varied diet, as well as a suitable aquarium environment. It is also important to ensure that the fish is obtained from a reputable dealer to avoid purchasing a wild-caught specimen, which can be detrimental to wild populations. Overall, the Royal Angelfish is a stunning addition to any marine aquarium and a joy to watch swim in the clear waters of the coral reef.