Longfin Bannerfish Heniochus acuminatus

The Longfin Bannerfish, also called the Pennant Coralfish, is native to tropical and subtropical reefs of the Indian and Pacific Oceans, from East Africa to Polynesia.

Bannerfish are related to Butterflyfish. The Longfin Bannerfish is very similar to the Schooling Bannerfish, H. diphreutes. The former lives in pairs but does also school, like the latter. Main visual differences are the corner of the anal fin, which is slightly rounder and with a larger white area on the former (the latter is more angular and the black and white division meets right in the corner of the fin) and the snout, which is slightly longer on the former.

Adults can reach 15-25cm long (the Schooling Bannerfish is 18-20cm). Above left are thought to be juveniles with short streamers. Apologies for the filthy public aquarium glass on the examples above centre and right, but I include them as they have a very even distribution of black and white on their slightly rounded anal fin corner.