Belonoperca chabanaudi
A small, secretive reef predator most often logged around Sulawesi, Indonesia, in warm 26 to 29 C water. Here's how to spot one and where to look.
A stocky little fish, rarely more than 10 cm, with a dark brown to purplish body broken up by pale blotches and a distinctive light arrowhead-shaped mark running up the head, which gives it its name. It has a heavy-set, almost grouper-like body shape for its size, with a slightly humped forehead and rounded fins. Most divers spot it tucked into a crevice or under a ledge rather than out swimming in the open, so the head marking and stocky silhouette are usually the first clues.
Expect to find it wedged into a crevice, under a coral ledge, or tucked against a wall rather than cruising the open reef, which is a big part of why it's logged as uncommon at most sites. It tends to sit still and let divers pass rather than bolt, so a slow look into likely holes on a wall or bommie is often what turns one up. Night dives and careful scanning of shaded overhangs improve your odds.
Soapfish in this family get their name from a bitter, toxic skin secretion (a defence chemical called grammistin) that deters predators, so its shy, tucked-away habit doubles as a low-risk lifestyle for a small fish with few other defences.
Sightings show no clear seasonal pattern, and the fish sits comfortably in the 25.8 to 28.8 C range typical of these tropical reefs year-round, so any month is fair game. Plan around the site conditions in Sulawesi, Palau or Pohnpei rather than around a soapfish season.
This is very much a Coral Triangle and Micronesian fish: it's most commonly logged around Sulawesi in Indonesia, with further reliable sightings in Palau's Rock Islands and Peleliu, and around Pohnpei in Micronesia. Indonesia carries the bulk of the recorded sightings, so Sulawesi is the strongest bet if you're specifically hunting for one.
Mapping where Arrowhead Soapfish is logged…
Sulawesi in Indonesia is the strongest region for this fish, with further sightings around Palau's Rock Islands and Peleliu, and Pohnpei in Micronesia. Outside these areas it's rarely reported.
There's no detected seasonal pattern, and the species sits in warm 25.8 to 28.8 C water year-round on these reefs, so it can turn up on any dive trip to Sulawesi, Palau or Pohnpei.
Look for a small, stocky fish around 10 cm long, dark brown to purplish with pale blotching and a pale arrow-shaped mark on the head. It's usually found wedged into a crevice or under a ledge rather than swimming openly.
They stay small, typically around 10 cm long, which along with their habit of hiding in holes makes them easy to miss on a reef.
No, they pose no threat to divers. Like other soapfish, they rely on a bitter skin toxin to deter predators rather than any aggressive behaviour.
Its skin produces a bitter toxic mucus called grammistin, a chemical defence typical of soapfishes that lets a small, slow-moving fish get away with sitting still in plain view of predators.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
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