Silver Moony

The silver moony (Monodactylus argenteus) is a moonyfish of the family Monodactylidae. The World Register of Marine Species (WoRMS) lists Monodactylus argenteus (Linnaeus, 1758) as the accepted name, and FishBase places it in the same family. FishBase and Wikipedia both list diamondfish among its common names, alongside butter bream and silver moonyfish; FishBase's English name is silver moony.

FishBase describes a short, deep, compressed body and gives a maximum length of 27 cm (standard length) and a common length of 12 cm. Wikipedia describes it as bright shiny silver with yellowish edges to the fins and black tips to the dorsal and anal fins; juveniles are more yellow and have two vertical black bands, one across the eye and one just behind the gill cover.

FishBase lists the species as Least Concern on the IUCN Red List (version 2025-2, global; assessed 28 June 2016).

FishBase gives its range as the Indo-West Pacific, from the Red Sea and the east coast of Africa and the Persian Gulf to Samoa, north to the Yaeyama Islands and south to New Caledonia and Australia, with a depth range of 0 to 12 m. FishBase says it is found in bays, mangrove estuaries, tidal creeks and the lower reaches of freshwater streams, and occasionally on silty coastal reefs; usually only juveniles enter fresh water. Wikipedia adds that it tolerates a wide range of salinities.

Where Divers Find Them

At Amed, Bali, Amed Jepun Divers describes a "school of diamondfish" on the left side of Jemeluk Bay and lists diamondfish among the bay's frequent encounters. The operator names the fish only as diamondfish; this entry follows the common name to Monodactylus argenteus, and no source cited here identifies the Jemeluk fish to species.

FishBase says it is commonly seen in large schools, while small juveniles are solitary or in small groups, and that it feeds on plankton and detritus. FishBase calls it highly territorial; Wikipedia says it shows territorial behaviour and can be solitary or form schools.

Underwater Encounter Behavior

The sources cited here do not describe how the silver moony reacts to divers. FishBase lists it as harmless to humans.