Chaetodontoplus poliourus
A small, uncommon angelfish of Sulawesi and Luzon reefs, seen year-round in warm 28-30C water at 1-20m depth.
A small angelfish, topping out around 5 cm, with a dark charcoal-grey body that fades to a pale, almost translucent grey tail, giving the species its name. Look for a narrow yellow rim along the dorsal and anal fins and a compact, deep-bodied shape typical of angelfish darting between coral heads. Its small size and understated grey tone make it easy to miss against reef rubble and shaded overhangs.
Divers typically find it working alone low on the reef, picking at algae and encrusting growth on coral rubble and rocky ledges rather than out in open water. It tends to stay close to shelter and can be shy, easing away from divers rather than approaching, so a slow, low approach and patience pay off more than chasing it. Logged as uncommon even at sites where it occurs, so a sighting is worth noting rather than expecting.
It belongs to a genus of angelfish that feed largely on algae and sponge material scraped from the reef surface, a diet that keeps them tied closely to a patch of reef rather than roaming widely.
No clear seasonal pattern shows up in the data, and its comfort range of 28 to 29.7C matches Coral Triangle reefs all year, so it is a fair year-round target rather than a seasonal one.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most consistently logged across Sulawesi in Indonesia and Luzon, Palawan, Mindanao and the Visayas in the Philippines, with a solid secondary population in Sabah, Malaysia and around Micronesia. Smaller numbers turn up in Papua New Guinea, Brunei, Palau and the Solomon Islands, making this a Coral Triangle specialist rather than a species you will find on a wider tropical spread.
Mapping where Greytail Angelfish is logged…
Best chances are across the Coral Triangle: Sulawesi in Indonesia, and Luzon, Palawan, Mindanao and the Visayas in the Philippines. Sabah in Malaysia and reefs across Micronesia also produce sightings, though it stays uncommon even there.
There is no strong seasonal signal in sighting data, and water temperatures of 28 to 29.7C hold year-round on its home reefs, so any month is reasonable for a sighting.
Look for a small, deep-bodied angelfish around 5 cm with a dark grey body that lightens sharply into a pale grey tail, plus a thin yellow edge along the dorsal and anal fins. It usually stays low near rubble or ledges rather than swimming in open water.
They stay small for an angelfish, reaching only around 5 cm in length, which combined with their muted grey colouring makes them easy to overlook on a reef.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
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