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Phylum Chordata > Subphylum Vertebrate > fishes > Family Monacanthidae
Fan-bellied filefish
Monacanthus chinensis*

Family Monacanthidae
updated Sep 2020

Where seen? This well camouflaged filefish is commonly seen on many of our shores, in sheltered areas with seagrasses and near reefs. It often remains motionless next to seaweeds or rocks, sometimes flattening out against or 'wrapping around' sponges, rubble and other large objects.

Features: To about 38cm, but those seen were 5-8cm long. Large triangular skin flap on the belly that can be greatly expanded, but often tucked close to the body. Body with lots of small circular dots and broad diagonal bars on the sides, in some these bars may be indistinct. It comes in all shades from brown to green. Tail fin large broad with thin brown bands. On a large adult, the upper fin rays on the tail is produced into a filament. More on how to tell apart filefishes.

Often with pattern of broad diagonal bars.
Chek Jawa, Jul 03

Tiny ones may resemble seagrass blades!
Changi, May 11

Looks like seagrass!
Changi, Jul 07

Large adults with filament on upper fin ray of the tail.

Filament on upper fin ray of the tail.
Chek Jawa, Sep 01
What does it eat? It eats seagrass, seaweed and small crustaceans as well as immobile animals such as bryozoans, ascidians and hydroids.

Human uses: It is sold as seafood in some places.

Some resemble coral rubble.
Chek Jawa, May 05

Three filefishes, head down among seaweeds.
Chek Jawa, Jul 05

Wrapped closely around a sponge.
Chek Jawa, May 04

*Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display.

Fan-bellied filefishes on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Punggol, Aug 22
Photo shared by Kelvin Yong on facebook.

Changi-Loyang, Jul 20
Photo shared by Dayna Cheah on facebook.

Changi Carpark 7, May 21
Photo shared by Loh Kok Sheng on facebook.

Berlayar Creek, Oct 15
Photo shared by Loh Kok Sheng on facebook.

Sentosa Serapong, Jul 15
Photo shared by Jonathan Tan on facebook.

Pulau Semakau, Jul 16
Photo shared by Marcus Ng on flickr.

Terumbu Semakau, Apr 13
Photo shared by Loh Kok Sheng on flickr.

Terumbu Raya, Aug 14
Photo shared by Loh Kok Sheng on his blog.



  • Allen, Gerry, 2000. Marine Fishes of South-East Asia: A Field Guide for Anglers and Divers. Periplus Editions. 292 pp.
  • Lieske, Ewald and Robert Myers. 2001. Coral Reef Fishes of the World Periplus Editions. 400pp.
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