Most juveniles begin color transition around 3.5–4 inches (9–10 cm) and complete it by 6–7 inches, usually between 12–24 months of age depending on diet and stress. Early signs include: the blue-and-white rings on the body breaking up, a darkening of the head, and faint yellow/green patches appearing along the dorsal area and flanks. Increased grazing on rock and a slightly bolder attitude toward tankmates often coincide with this change. Stable water quality, high-quality marine angelfish pellets, nori, and sponge-based frozen foods will help reduce stress lines and patchy coloration during the transition.

Newly imported juveniles often “glass surf” because they are used to open reef and rock faces, not closed glass walls. To get them eating: • Provide live rock with natural algae and microfauna for grazing. • Start with small, frequent feedings of clam on the half shell, finely chopped shrimp, mysis, and spirulina brine. • Rub frozen food onto rock crevices so it mimics natural picking behavior. • Add a small, peaceful dither fish (like chromis) that eats aggressively; many angels copy this. Usually within 3–7 days they associate you with food and begin taking pellets/flake; persistent refusal beyond 10–14 days warrants checking for parasites or internal issues.

Juvenile Korans are omnivorous pickers with a strong tendency to sample soft, fleshy textures. Zoanthids and LPS (acans, blastos, euphyllia, trachyphyllia) resemble the polyps, tunicates, and sponges they graze in the wild. SPS have tougher tissue and less movement, making them less attractive. While individual fish vary, most juveniles become more coral-destructive as they grow. To reduce coral damage: keep the fish well-fed with varied foods rich in sponge and algae, provide lots of natural grazing surfaces, and avoid prized zoa/LPS colonies in the same tank. For long-term reef systems, this species is best treated as “not coral safe.”

Although a small juvenile can be started in a 90–120 gallon tank, long-term housing should be at least 180 gallons (6 ft/180 cm length) with a larger footprint preferred. This species grows to about 10–12 inches and needs: • Long, unobstructed swimming lanes along the front and back. • A central or back-wall rock structure with multiple swim-throughs and caves for security. • Vertical rock faces with plenty of surface area for grazing. Avoid narrow “rock wall” layouts that cut the swimming path in half. Juveniles raised in cramped or cluttered tanks often show stunted growth, ragged fins from bumping rock, and increased aggression.

Juvenile coloration can sometimes reduce initial aggression because other angels may not recognize it as the same species or as a future large rival, but this is temporary. For mixed-angel setups: • Add the Koran juvenile after smaller dwarfs (e.g., flame, coral beauty) but before larger aggressive angels (e.g., queen, passer). • Use a tank of 220+ gallons with lots of rockwork and multiple feeding stations. • Avoid mixing it with another Pomacanthus semicirculatus or very similar large Pomacanthus to minimize hybridization and severe fights as they mature. Expect hierarchy skirmishes once your Koran nears adult size and coloration; watch for persistent chasing, fin tears, or refusal to let subordinates feed, and be prepared to re-home the aggressor if needed.