Helcogramma striata
A 2cm reef fish common on Malaysia's east coast and Raja Ampat, easy to miss but easy to ID once you know where to look.
At just 2cm, this is a fish you spot by pausing and scanning rubble and coral rather than swimming past it. Look for a slender, almost cylindrical body carrying dark longitudinal stripes running head to tail, and the diagnostic three separate dorsal fins that give all triplefins their name. It tends to perch upright on a fin base rather than swim in open water, which is often the first clue you have found one rather than a blenny.
Watch a patch of dead coral or rubble for a minute and you will likely see one dart a few centimetres, stop, and hold dead still on its pelvic fins, using them almost like a tripod. It shows little concern for divers at typical viewing distance, since its main defence is simply blending into the substrate rather than fleeing. Most sightings come from slow, close-focus looks at reef structure rather than mid-water encounters, so it rewards divers who work macro rather than cruise past.
Triplefins get their name from having three distinct dorsal fins rather than one continuous one, a feature you can actually pick out on a fish this size if you get close and steady your buoyancy.
No clear seasonal pattern shows up in the sightings, and with a comfortable range of 25.1 to 29.3C it has no reason to disappear in any particular month. Treat it as a year-round find on Indo-Pacific reefs rather than something tied to a dive season.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
This is most reliably logged on Malaysia's Peninsular East Coast, where sightings far outnumber anywhere else in the data, followed by strong numbers across Indonesia in Raja Ampat, Sulawesi and Nusa Tenggara. Thailand's Khao Lak and Phuket, plus the Philippines' Visayas and Luzon, also turn up consistent records, with a scattering of sightings in Australia, the Solomon Islands and the Marshall Islands.
Mapping where Striped Triplefin is logged…
Best odds are on Malaysia's Peninsular East Coast, which logs far more sightings than anywhere else, plus Raja Ampat, Sulawesi and Nusa Tenggara in Indonesia. Khao Lak and Phuket in Thailand and the Visayas and Luzon in the Philippines are also solid bets.
There is no detected season in the sighting data, and its warm-water niche of 25.1 to 29.3C is met year-round across its Indo-Pacific range, so any month works.
Look for a tiny (about 2cm) slender fish with dark stripes running along its body, perched motionless on rubble or coral rather than swimming freely. The three separate dorsal fins, visible up close, confirm it as a triplefin rather than a blenny.
Around 2cm as adults, making them one of the smaller reef fish a diver will try to photograph. You need to get close and hold still to appreciate the stripe pattern.
No. They are harmless carnivores feeding on tiny invertebrates and pose no risk to divers; the only challenge is spotting them.
Like other triplefins, it has three separate dorsal fins instead of the single continuous fin most reef fish have, a feature worth checking for once you have located one.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Malacoctenus triangulatus
Klipfish
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