Stegastes nigricans
Small brown damselfish tending algae turf in Egypt's Marsa Alam, Mauritius and the Society Islands year-round in 25-29C water.
A stocky, oval-bodied damselfish about 9 cm long, coloured dark brown to almost black with faint darker scale edges giving a scaly texture. Look for a small, blunt head and a habit of hovering close to a patch of turf algae it will not leave. Juveniles show more contrast, with a pale blue or whitish tinge along the upper body and fins that fades with age.
Spend most of a dive stationed over a patch of turf algae on the reef flat or shallow slope, rarely straying far from that spot even as divers pass close by. They actively weed out unwanted algae species and will dart at intruders, including divers, that get too near their patch, though the aggression is all bluff at this size. Most sightings are shallow, from the surface down to around 12 metres, in reef-flat and lagoon habitat.
Farmerfish cultivate their own algae "gardens" by weeding out unpalatable species and aggressively chasing off grazers, a real example of a fish practising monoculture farming on the reef.
No clear seasonal pattern shows up in the data, and with a comfortable range of 25 to 29.3C across its Indo-Pacific reefs, it is there to find on any dive year-round.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged in French Polynesia, especially the Society Islands, and a strong sighting across Egypt's Red Sea Riviera and Marsa Alam region. Also a common find in Mauritius around Flic-en-Flac, and reported steadily from Fiji, Reunion, the Seychelles' Inner Islands, the Maldives' Central Atolls and New Caledonia.
Mapping where Dusky Farmerfish is logged…
French Polynesia's Society Islands and Egypt's Marsa Alam and Red Sea Riviera are the strongest spots, with reliable sightings also in Mauritius, Fiji, Reunion, the Seychelles and the Maldives.
There is no strong season in the sighting data. They live in warm water year-round, so any dive trip to their reefs should turn one up.
Look for a small, dark brown, oval-shaped damselfish hovering stubbornly over one patch of algae turf. It rarely swims far from that spot, which is a strong clue alongside its plain dusky colour.
They stay small, reaching around 9 cm, so most divers spot them by their behaviour and habitat rather than size.
They tend and defend a patch of turf algae, weeding out species they do not want and chasing off other fish, effectively farming their own algae garden on the reef.
No. They may dart at a diver who lingers over their algae patch, but this is territorial bluffing rather than any real threat, and there is no danger from handling or proximity.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Yellowtail Clownfish
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