Schooling Bannerfish

Heniochus diphreutes

Also known as False Moorish Idol, Pennant Butterflyfish, Pennant Coralfish

SaltwaterFish

Schooling Bannerfish (Heniochus diphreutes) — NPS photo - Bryan Harry · Public domain

Care at a glance

Temperature: 75–81°F (24–27°C)
pH: 8.1–8.4
Adult size: 8.3 in (21 cm)
Minimum tank: 124 gal (470 L)
Temperament: Peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Easy
Breeding: No record
Rarity: Common
Reef safe: Reef safe
Origin: Indo-Pacific reefs, from East Africa and the Red Sea to Hawaii and Polynesia, south to the Kermadec Islands
Family: Chaetodontidae

Overview

Peaceful with other fish and, true to its name, does best kept in a group introduced to the tank at the same time, where it shoals together rather than fighting over territory. It is reef safe and generally leaves corals, anemones, and gorgonians alone as long as it is well fed, though a hungry fish may pick at ornamental shrimp or other small invertebrates. It adapts to aquarium life more readily than most butterflyfish and accepts frozen mysis, krill, and other prepared foods without much fuss, but still benefits from two or three feedings a day given how much it eats in the wild.

In the wild

Ranges across the Indo-Pacific from East Africa and the Red Sea to Polynesia and Hawaii, north to southern Japan and south to the Kermadec Islands, typically over deep reef slopes and drop-offs where it gathers in large aggregations to feed on plankton in the current. It spends most of the day swimming well off the bottom, so it needs a long, open tank with plenty of vertical swimming room as well as live rock for shelter at night. A single fish needs at least 470 litres (125 US gal), and a school needs considerably more space to spread out.

Good to know

Carries the long, trailing white dorsal filament and bold black-and-white banding typical of genus Heniochus, and is often nicknamed the false moorish idol or poor man's moorish idol for its resemblance to the unrelated Zanclus cornutus. It is easily confused with the similar longfin bannerfish, Heniochus acuminatus, but has a rounder chest profile and a shorter snout, and unlike its relative it is a dedicated open-water plankton feeder rather than a bottom-picking generalist. Reaches around 21 cm.

Did you know

Buyers shopping for this species should look closely at what they are getting: it is so easily confused with the longfin bannerfish that fish sold under the schooling bannerfish name sometimes turn out to be the less reef-friendly acuminatus once they arrive, since telling the two apart takes a side-by-side look at snout length and chest shape.