Butterflyfishes are some of the most eye-catching fish in the aquarium hobby. The pennant bannerfish (Heniochus acuminatus) closely resembles the elegant Moorish idol (Zanclus cornutus). Many older hobbyist manuals even refer to this fish as the “poor man’s Moorish idol.” This stigma is a shame because the pennant bannerfish is not only quite striking on its own, but it is a much better aquarium fish than almost any other butterflyfish available. Heniochus acuminatus is found throughout the western Indo-Pacific and is collected from a number of different countries. It has thick alternating white and black vertical bars, and yellow dorsal, caudal and pectoral fins. The most distinctive feature of this fish is the long white pennant along its elongated first dorsal spine. While it is also known as the black and white butterflyfish, wimplefish and longfin bannerfish, it will most often appear in aquarium shops simply as theHeniochus butterfly. Although it usually transitions well eventually, this species is often prone to shipping stress, including external parasites. Look for white spots, especially on the pectoral fins and on the black bars of this fish. Healthy fish will have clear eyes and a good body weight. Torn fin tissue can often heal, but the delicate dorsal banner will not regenerate if the actual bone ray is missing. Ideally, all fins should look healthy and intact; handle them gently to maintain health through transport and quarantine. Provide a spacious quarantine system to help the fish feel comfortable and keep it from tearing its fins if it thrashes around. Specimens should be observed in quarantine for several weeks and will tolerate prophylactic internal medicines and copper therapy.
Aquarium requirements: Pennant bannerfish can grow to 8 inches. Given their somewhat delicate build, larger tanks are preferable to smaller ones, and adults should have a system of several hundreds of gallons. Juveniles can be smaller than 2 inches total length but will quickly grow to a “medium” size of 3 to 4 inches. Keep medium-sized specimens in 90 gallons and up. Bannerfish in confined spaces will usually tear their dorsal fins, risking infection. Thus, more space is always better with this fish. Heniochus butterflyfish are best-suited to a fish-only system, and they can tolerate water quality associated with slightly more dense fish populations. Stable tropical temperatures between 74 and 80 degrees Fahrenheit are required. Specific gravity should be kept around 1.020 to 1.024, with good water circulation to boost daytime pH above 8.0. Provide adequate biological filtration to keep ammonia and nitrite at undetectable levels, and perform regular water changes to keep nitrate below 25 parts per million. Ultraviolet sterilization will aid in water clarity and prevent parasite transmission.
Compatibility: This species is not aggressive, though it may be territorial with other members of the species. Many hobbyists are tempted to display this fish in schools, but this requires space and is outside the range of most home tanks. To be safe, keep only one per tank. One important element for keeping H. acuminatus is selecting tankmates that won’t nip at its trailing fins. This rules out chronic fin-nippers, such as many triggerfishes, damselfishes and some angelfishes. Good tankmates are typically peaceful species, such as wrasses, dwarf angels and chromis.Heniochus acuminatus is not considered reef- safe, and it should not be placed into a community with sessile invertebrates. It is, however, typically safe with crabs, shrimp and snails.
Feeding: While nutrition is usually the biggest hurdle in keeping most butterflyfishes, bannerfish are generally more responsive to aquarium fare. Feed them Mysis shrimp and other meat and plankton foods, as this makes up the majority of their wild diet. Soak frozen foods in vitamins to help prevent head and lateral line erosion (HLLE).Heniochus acuminatus accepts plant-based foods, such as dry seaweed flakes (nori), and well-acclimated specimens will often accept dry foods, such as flakes or soft pellets.
Notes: While H. acuminatus is not considered reef-safe, its close cousin H. diphreutes is more likely to behave in a system with corals. It is difficult to identify a fish individually, however, and unless they are side-by-side, it is easy to mix them up. I recommend avoiding this genus altogether if corals are a priority in the system. These two species are not the only attractive fish in the genus, and there are many species in the trade that are suitable for fish-only tanks. Examples include H. monoceros, H. chrysostomus and H. intermedius. FAMA.