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Acanthurus japonicus

Acanthurus japonicus is a surgeonfish (family Acanthuridae) 1 recognisable by the broad white band between the eye and the upper lip and by the orange band on the dorsal fin. 2 4 It lives between Indonesia, the Philippines and southern Japan, in shallow, clear water, where it feeds on algae. 2 4

AcanthuridaeIUCN: Least concern
Acanthurus japonicus

At a glance

Data from the scientific sources listed at the bottom.

Depth in the wild

5–15 m

0 m4 m8 m12 m16 m20 m

Size

up to 23 cm

0612182430

maximum total length

Temperature in the wild

24–28 °C

18 °C34 °C

Where it lives

Red SeaWestern Indian OceanEastern Indian OceanCentral Indo-PacificWestern PacificCentral PacificEastern PacificWestern AtlanticEastern AtlanticMediterranean

From Sulawesi (Indonesia) to the Philippines and the Ryukyu Islands. 2 FAO sums up the range as Indonesia to southern Japan. 4

Conservation

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IUCN Red List: least concern (2010). Red List data taken from FishBase. 2 FishBase states that the species is not assessed by CITES, and a search on Species+ gives no results. 2 7 In the United States, together with Acanthurus leucosternon, it makes up most surgeonfish imports apart from Paracanthurus hepatus, which accounts for about half of them. 6

How to recognise it

Tap a number on the photo: the key explains what to look for.

1234
  1. 1Band below the eye broad, from the lower edge of the eye to the upper lip; it is white, here it looks blue because of the lights 2 4
  2. 2Orange band on the dorsal fin in the outer part of the soft section of the fin 2 4
  3. 3Yellow pectoral fin base in A. nigricans it is black instead 2 4
  4. 4Yellow tail peduncle fading to black further forward 2 4

Life in the wild

Where it is found

Lagoons and reefs facing the open sea in clear water, usually in shallow, exposed areas. 2 FishBase gives an overall range of 1-20 m. 2

What it eats

It feeds on algae. 2

Behaviour

It forms small to large groups, but sometimes lives alone. 2

Reproduction

It has separate sexes and fertilisation takes place in the water, outside the body: the eggs are scattered and receive no parental care. 3 This comes from a general FishBase classification: no studies on the reproduction of this species are documented, nor is the size at maturity. 2 3

In the aquarium

From the experience of the BallingMania community.

Community rating
Level in the tank
lowmediumhigh
Coral compatibility
lowmediumhigh
Aggression
lowmediumhigh
Care difficulty
lowmediumhigh
Original sheet

A fish belonging to the family Acanthuridae, an animal found in the western Pacific Ocean, that is in Indonesia, the Philippines and the Coral Sea. A hardy fish with a peaceful temperament, but it cannot live with others of its kind or other Acanthurids, especially Acanthurus nigricans and Acanthurus leucosternon. In the wild it lives along outer reefs, in coastal areas and in lagoons, at depths ranging from 5 to 20 metres. The body is a reddish light brown tending to mustard yellow with a yellow line, the area between the eye and the mouth is pale, the fins are black edged with turquoise, the caudal fin is pale, white or yellow, and finally it has a red sickle-shaped mark at the end of the dorsal fin. Like all surgeonfish, on the caudal fin it has the classic "scalpels", very sharp bony structures pointing forwards.

To keep it in a tank, excellent water quality is needed; in optimal conditions it is an animal resistant to disease; it suffers from low pH and excessive concentrations of nitrate and phosphate; it loves a strong flow, preferably alternating and intermittent. When stressed it is prone to attacks of Oodinium and to fungal skin infections; an animal prone to intestinal worms.

Given its size, it must be kept in large tanks from 500 litres upwards; room for swimming is essential, with crevices among the rocks to take refuge in. Fairly difficult to acclimatise, but once well settled in it is omnivorous; it prefers dry or granular food, frozen food such as Artemia and chironomus, Nori seaweed, lettuce leaves and boiled spinach. It does not refuse rounds of banana and sliced courgettes.

Species sheet by Massimo Ramognino and photo by Emanuele Puoti Fcim

Did you know?

It is very close to Acanthurus nigricans: where the ranges meet the two interbreed, and genetics separates them only at the level of population or subspecies. 5 In 98% of the fish in the whole study, however, the mitochondrial DNA matched the species indicated by appearance, a sign that the species may not be losing their identity. 5
FAO tells them apart like this: A. nigricans has a horizontal white spot below the eye and a black tail peduncle, A. japonicus a white band reaching the lip and a yellow peduncle. 4

Sources

  1. Froese R., Pauly D. (eds.), via WoRMS (2026). Acanthurus japonicus (Schmidt, 1931). World Register of Marine Species.
  2. Froese R., Pauly D. (eds.) (2026). Acanthurus japonicus, Japan surgeonfish. FishBase.
  3. Froese R., Pauly D. (eds.) (2026). Reproduction of Acanthurus japonicus. FishBase.
  4. Randall J.E., in Carpenter K.E., Niem V.H. (eds.) (2001). Acanthuridae. The living marine resources of the Western Central Pacific, vol. 6. FAO.
  5. DiBattista J.D., Whitney J., Craig M.T., Hobbs J.-P.A., Rocha L.A., Feldheim K.A., Berumen M.L., Bowen B.W. (2016). Surgeons and suture zones: Hybridization among four surgeonfish species in the Indo-Pacific with variable evolutionary outcomes. Molecular Phylogenetics and Evolution, NOAA record.
  6. Veríssimo D., Anderson S., Tlusty M. (2019). Did the movie Finding Dory increase demand for blue tang fish?. Ambio.
  7. UNEP-WCMC (2026). Search for Acanthurus japonicus in the CITES lists. Species+.

Sources checked on 5 November 2026. Community texts and ratings are kept separate from the scientific data.

View the original sheet (Italian)All species