All fish / Zenarchopteridae

Duncker's halfbeak

Zenarchopterus dunckeri

Also known as duncker's river garfish, duncker's half beak, dunker's halfbeak, river garfish, brackish halfbeak, todak, julung-julung, 邓氏异鳞鱵

A slim, silvery greenish surface fish with a long fixed lower jaw and a short upper jaw, typical of halfbeaks. Males have modified, elongated fin rays in the anal and dorsal fins. It is kept for its unusual shape and lively surface behaviour in mangrove and estuary style tanks.

Care at a glance

Care level

Moderate

Temperament

Semi

Adult size

10 cm

Temperature

24 to 28 °C

pH

7 to 8.2

Smallest tank

120 litres

Keep as

Group of 5 or more, ideally with more females than males

Diet

Carnivore: live and frozen insects such as fruit flies and mosquito larvae, brine shrimp, bloodworm and floating flake

Swims

Top of the tank

Lifespan

2 to 4 years

Water

Brackish

Wild range

Indo-West Pacific: Sri Lanka and Thailand east to Indonesia, the Philippines, New Guinea and northern Australia

Breeding

Fertilisation is internal, with males using a modified anal fin, but females lay eggs rather than giving birth. Captive breeding is occasional and fry need tiny live foods in clean brackish water.

Good to know

Very jumpy and easily injures its fragile beak on glass, so use a tight lid and avoid sudden disturbances. It does best in brackish water and may eat very small fish or fry at the surface.