Blue Koran Angel (Pomacanthus Semicirculatus)

Also Known As: Koran Angelfish, Semicircle Angelfish

Compatibility and Behavior
The Blue Koran Angel (Pomacanthus semicirculatus) is one of the more dramatically transforming fish in the hobby — juveniles and adults look so different that it's genuinely hard to believe they're the same species. Juveniles arrive with deep blue to nearly black bodies crossed by narrow, bright blue and white curved bands that arc across the body like stylized script. As they mature, that pattern gives way to something entirely different: an olive-green to yellow-brown body densely speckled with blue, each scale edged in electric blue, with vivid blue-trimmed fins, and trailing filaments on the dorsal and anal fins. Under strong reef lighting, the Blue Koran Angel is a truly regal fish.
That said, this is not a reef-safe species. It commonly nips at LPS corals, soft corals, clam mantles, and certain sessile invertebrates, and it becomes increasingly territorial as it matures — particularly toward other large angels or similarly shaped tankmates. A fish-only or FOWLR setup where it can be the undisputed centerpiece is where it belongs.

Aquarium Requirements
Blue Koran Angels in the 1–4 inch range can be started in a well-established system of around 90–120 gallons, which gives them room to grow, establish some territory, and behave naturally without being overwhelmed by a cavernous display…or becoming too territorial in a smaller tank. Just know that this fish can grow fairly large over time, so the bigger the tank, the better. Extensive rockwork with arches, overhangs, and caves supports its natural grazing behavior and gives it territory to claim, while open swimming space lets it cruise comfortably. Strong, well-oxygenated flow and robust filtration are important regardless of the fish's current size. Diet should center on high-quality sponge-based angelfish preparations and marine algae sheets, supplemented with mysis, chopped seafood, and quality pellets to support healthy growth and immune function.

Specifications
Approximate Size: Sm: 1-2", Smd: 2-3", Md: 3-4", Lg: 4-5"
Diet: Omnivore; sponge-based angelfish formulas, marine algae, mysis, chopped seafood, quality pellets
Origin: Indo-West Pacific, including Red Sea to Fiji, Japan to Australia
Care Level: Intermediate
Reef Safe: No; known to nip at corals, clams, and sessile invertebrates
Temperament: Semi-aggressive; increasingly territorial as it matures/grows, especially toward other angels
Minimum Tank Size: 90–120 gallons for juveniles; larger system required as fish grows
Special Considerations: No special substrate requirement; best kept singly as the primary large angelfish; requires excellent water quality, strong filtration, and careful tankmate selection; juvenile and adult coloration differ dramatically