White-cheek Tang (Acanthurus japonicus): Breeding Guide
Acanthurus japonicus is a pelagic broadcast spawner that releases gametes into the open water column over reefs. Its planktonic acronurus larvae cannot be reared in home aquaria, so captive breeding is not realistic.
Overview
Acanthurus japonicus, the White-cheek Tang, is a Western Pacific surgeonfish recorded from Sulawesi and the Philippines north to the Ryukyu Islands. FishBase lists a maximum total length of about 23 cm, with most individuals seen between 5 and 15 m on clear lagoon and seaward reefs. Like all members of the genus, it carries a single retractable spine on each side of the caudal peduncle.
It occurs solitarily or in small to large feeding aggregations and grazes filamentous algae. There are no documented cases of this species being spawned and raised through to settlement in a private aquarium.
Spawning Behavior & Trigger
Surgeonfishes of the genus Acanthurus are pelagic broadcast spawners. Spawning typically occurs at dusk in brief pair- or group-spawning ascents into the water column, often concentrated around the outer edge of fringing reefs or near reef passages. Many species gather to spawn when water warms, frequently around the full and new moon, with tidal currents helping carry the gametes off the reef.
Fertilization is external: males and females release sperm and eggs into open water during a rapid upward rush. Species-specific spawning data for A. japonicus has not been published in the consulted sources, so the description here reflects the general Acanthurus pattern.
Egg & Fry Care
Eggs and larvae are pelagic. The fertilized eggs float and hatch into transparent, scaleless acronurus larvae that are well adapted to open-ocean life and may remain in the plankton for more than 39 days before settling onto a reef.
This long planktonic phase, combined with the larvae's reliance on natural ocean micro-plankton, is why home rearing is not achievable. Only research aquaculture facilities have attempted larval rearing for any surgeonfish.
Common Challenges
- Gametes are scattered in open water, so no pair bond or nest forms that an aquarist could manage.
- Acronurus larvae require weeks of pelagic drift and specialized plankton not available in tanks.
- Adults reach over 20 cm and are semi-aggressive toward similarly shaped tangs, making conditioning a compatible pair impractical.