All fish / Monacanthidae

Hair-finned Leatherjacket

Paramonacanthus japonicus

Also known as hairfinned leatherjacket, japanese filefish, hair-finned filefish, paramonacanthus filefish, ヨソギ, 日本副单角鲀

This is a small filefish with a flattened body, a stout first dorsal spine and blotchy brown and pale markings that it can change to match its surroundings. Males grow a filament on the second dorsal fin. Keepers like it for its odd shape and its habit of hovering among weed and rubble.

Care at a glance

Care level

Moderate

Temperament

Semi

Adult size

9 cm

Temperature

22 to 27 °C

pH

8.1 to 8.4

Smallest tank

150 litres

Keep as

Singly or as a pair

Diet

Carnivore: mysis, chopped shrimp, small crustaceans and frozen marine mixes

Swims

Middle of the tank

Lifespan

3 to 5 years

Water

Marine (saltwater)

Wild range

Western Pacific and eastern Indian Ocean: Japan, China, Southeast Asia to northern Australia

Breeding

It lays sticky eggs on the bottom or among weed, and the larvae drift in the plankton. Captive breeding is rarely achieved at home.

Good to know

It may nip at sessile invertebrates, small shrimps and the fins of slow fish, so it is not fully reef safe. Feed it several times a day as thin specimens struggle to recover.