Chaetodon octofasciatus
Spot the Eightband Butterflyfish in warm Coral Triangle waters. Most logged in Malaysia, Thailand, and the Philippines, here's when and where to find one.
Eight crisp, dark vertical bars across a white body are the defining feature, count them and you have your ID. The face carries a bold black eye-stripe, and the tail and rear of the body tend toward yellow. It is a small, laterally flattened butterflyfish, so it sits almost disc-shaped in the water column and often drifts close to branching coral heads. Juveniles share the same banding pattern as adults, making the species straightforward to identify at any life stage.
You will usually encounter it picking at coral polyps or small invertebrates among branching Acropora and other stony corals, it is a dedicated corallivore (coral polyp feeder) and rarely strays far from the reef structure. It tends to be seen in pairs or small groups rather than alone, and individuals stay close to the coral for cover rather than venturing into open water. It is not especially skittish but will slip into the coral if you approach too quickly, so slow, steady movements get you closest.
Because it feeds almost exclusively on live coral polyps, it is considered a useful indicator of reef health, healthy branching coral coverage tends to mean more eightband butterflyfish in the area.
Sightings are recorded across most of the year, concentrating from December through October with a relative quieter patch in November. The species favours water temperatures of around 27.5 to 30 °C, which are available on these tropical reefs for most of the calendar year.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most records come from Malaysia, particularly the reefs around Perhentian and Redang islands and Pulau Tioman, which together account for the lion's share of logged sightings. Thailand's Gulf of Thailand and Phuket area, plus Palawan and Apo Reef in the Philippines, are the next most reliable bets. Indonesia's Bali and Lombok, Cambodia's Koh Rong Archipelago, and Palau round out the core range in the Coral Triangle and surrounding seas.
Mapping where Eightband Butterflyfish is logged…
The strongest populations are logged in Malaysia around Perhentian, Redang, and Tioman, followed by Thailand's Gulf of Thailand sites and Phuket, and the Philippines around Palawan and Apo Reef. Indonesia, Cambodia, and Palau also produce regular sightings.
Sightings are spread across most of the year, broadly December through October. The species lives in consistently warm tropical water around 27.5 to 30 °C, so there is no single short season to chase, plan around local dive conditions at whichever destination you choose.
Count the dark vertical bars on the body, there are eight of them on a white background, which is what sets this species apart. A black eye-stripe and a yellowish tail region complete the picture. It is a small, disc-shaped fish almost always seen near branching corals.
Most diver logs record it as uncommon rather than common, so do not expect to see one on every dive. Your best odds are on healthy branching coral reefs in Malaysia or the Philippines, where it is recorded more regularly.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Melon Butterflyfish
1,616 sites
