Emperor Angelfish

The emperor angelfish is the best-known member of the large angelfish (Pomacanthus). Its oval body, which reaches 40 cm in adults, is covered in blue and yellow horizontal stripes; a black mask runs over the eyes and a dark band behind the gill cover. Juveniles look completely different: they carry concentric white and light blue rings on a navy background. The change begins at around 8–12 cm and is completed within months.

All individuals are wild-collected. This is a long-lived, large fish that needs a lot of space; before buying, make sure you have an aquarium suited to its adult size.

It lives in the Indo-Pacific and the Red Sea, on reefs with rich coral growth, around caves and overhangs. Juveniles live alone in more sheltered rock crevices. In the wild it feeds mainly on sponges and tunicates.

• Volume: at least 1000 liters and 200 cm of length for an adult; even if a juvenile starts in a smaller tank, the adult aquarium must already be planned.
• Water: salinity 1.023–1.026 specific gravity, pH 8.1–8.4, temperature 24–27°C. Since it is a large, polluting fish, it needs strong filtration, a good protein skimmer and regular water changes.
• Decor: a sturdy rock arrangement with caves and passages; swimming space should also be left.
• Reef compatibility: not reef safe. It picks at LPS and soft corals, zoanthids, Tridacna clams and tube worms. Some hobbyists take the risk with stony corals in very large systems; it is not recommended for beginners.

Omnivorous. Angelfish foods containing sponge, suited to its sponge-heavy diet in the wild, should be the staple. In addition, offer frozen mysis, chopped mussel and shrimp, dried seaweed and spirulina. 2–3 times a day.

Once settled into the aquarium it is bold and curious; it recognizes its keeper. It is aggressive toward its own kind and other large angelfish. It is known to make clicking sounds when threatened.

Good companions: in a very large aquarium, tangs, Heniochus, large wrasses, foxface, large damsels, calm triggerfish.

Avoid: other large angelfish, reefs with corals and Tridacna clams, small and timid species.

Keep a single individual in the aquarium. Two large angelfish can only be kept together at public-aquarium scale.

In the wild, pairs release pelagic eggs into the water column in the late afternoon. It does not breed in home aquariums.

• Head and lateral line erosion (HLLE): common in large angelfish; a varied diet and good water quality prevent it.
• Marine ich and velvet: quarantine is essential.
• Feeding problems: individuals stressed by shipping may refuse food in the first weeks; sponge-based foods and live rock stimulate the appetite.

The sexes cannot be reliably told apart externally.