Saltwater butterflyfishes are so hard to keep; they have narrow chemical and physical water quality tolerances, are finicky eaters & die for mysterious reasons....." This statement may be so for some species, especially for some of the coral-feeders, but certainly not for the butterflyfishes in the genus Heniochus. They are superbly adaptable aquarium specimens which acclimate quickly, thrive under a variety of conditions, are not quarrelsome & readily accept all foods.
The eight known species of the genus are members of the butterflyfish family Chaetodontidae, meaning "bristle teeth" in reference to their prising snout and dentition. All eight species are similarly shaped with laterally compressed sides, a pointed rostrum and a lengthened fourth dorsal ray. Their German common name is "Wimplefish" (like Wimple's piranha) meaning "Pennantfish" or "Bannerfish". A wimple is a type of hat with feathers of which the heightened dorsal is reminiscent.
For various structural similarities Heniochus spp. are considered derived from and closely related to another butterfly genus Hemitaurichthys which in turn is from the mega-genus Chaetodon.
Some brief notes on the various species:
Is best done from one dealer's tank, buying all the desired individuals of the genus and introducing them all at once. Though most Heniochus are not quarrelsome per species or individual, they can become territorial in small systems. Fifteen to twenty gallons of space per copy is a suggested minimum. Many species can attain a length of ten inches.
Buy smaller specimens (three to four inch in total length) if possible as these adapt best. Be wary of slightly smaller ones; particularly if they are thin of musculature between the eyes in the head region. These may eat, but not recover to full health.
The several species of Heniochus live in shallow water near the sea bed; typically near broken shorelines. Their slim bodies make them well-disposed to quick passage and safety between the rocks and corals of their wild environs.
They have a wide tolerance of salinities as butterflyfishes go, but appreciate one that are not too consistently low. 1.025-1.021 is a tolerable range. Higher pH's, 8.2-8.4 are recommended.
Chemical parameters are likewise not a problem with these species. They are more tolerant of endogenous pollution than most commonly kept aquarium species. Your charges will be healthier and live better, longer if you maintain better water quality. Use of a skimmer and the presence/culture of algae, like Caulerpa goes a long way in ensuring suitable water.
These butterflyfishes are social animals, being found in groups of a pair or more to veritable shoals of a few hundred individuals. It makes sense that they should not be kept solitarily if possible. Try to observe them in your dealer's tank and choose two or more that appear to associate readily. If room and/or finances restrict your selection, H. acuminatus seems to adjust best at being "the only Heni in the tank".
Heniochus as butterflyfishes in general, are not aggressive; they have neither the teeth or the body armament for it. If enough habitat is provided, they will gladly choose flight over fighting. Heniochus, between and among species, may "butt" with their head projections, but this is generally not dangerous.
Another bonus: some species have been observed to be facultative cleaners; especially as young. This is yet another example of a "can-do" parasite remover, other than more obligate cleaner wrasses or gobies.
Actual spawning behavior has not been observed in the wild or captivity for Heniochus or any Chaetodontid to date (Burgess, 1978). It is postulated that 3000-4000 eggs are released in a spawning and scattered by currents in the upper water column, i.e. they are pelagic.
Heniochus may be eaten by typical large predatory fishes in whose mouths they can fit. Be wary of basses, lionfishes, morays et al.. Though they are "quick on their fins " during the day, butterflyfishes "sleep" peacefully on the bottom in the evenings and may become midnight snacks.
Heniochus are largely plankton eaters in the wild. They readily consume frozen, flake, fresh, freeze-dried, seemingly whatever foods offered- even directly from the surface by hand.
These butterflyfishes should be fed a variety of foods as per the rest of their family; frequently, in small amounts, at least two, three times daily. Clean, pollution-free tubificid worms are relished, after the fish have been trained on them. Use live freshwater foods as an occasional high-protein treat.
Some vegetable matter should be offered in the diet; best if grown in the system itself.
Vitamin supplements are useful applied to the food or water directly; fructose sugar may even be applied to bolster an ailing specimen (Baensch in Allen & Steene, 1979) as marine fishes "drink" environmental water.
This genus is relatively disease free. They are susceptible, as are most tropical marine fishes, to the two most common coral reef parasitic "plagues": Amyloodinium and Cryptocaryon; displaying their typical symptomology (rapid breathing, listlessness, clamped fins). Most reports show Bannerfishes to be easily treated with manipulation of temperature and specific gravity, and no great sensitivity to common therapeutics, like copper compounds.
Various external parasites may be present and become problematical in recently captured wild specimens, if over-stressed. Gill flukes and parasitic copepod crustaceans may be reduced/alleviated through quarantine, dips or other chemical treatment. More appropriately, they might be biologically controlled through the use of a "cleaner" relationship.
One condition that Bannerfishes are prone to is "lateral-line disease". Regardless of where you stand on the debates of "original" cause(s) (Vibrio, other bacteria, water quality, diet, genetics, combo, ...) this disease can lead to death within a few days. What to do? Standard Operating Procedure: Pick out healthy stock; ascertain that they've been at your dealer's at least a few days... or put down a deposit and leave them. Ask to see them eat what you're going to feed. Run them through a disinfecting freshwater dip. Acclimate to a viable system. Keep your organic load low..... & if your fish should begin "breaking down" I suggest a regimen of medicated food, such as Tetra (tm) or Sera's (tm) line of antibiotic-fortified prepared flake foods. Gram-negative antibiotics and Furacyn compounds have been found to be effective.
What about the specialized Tholichthys larvae of these species with their bizarre spines? Chaetodontids and Scatophagids (scats) are the only families with this trait. Will you be the first to spawn and rear or even just observe and photograph spawning in the wild?
By any and all means try this genus. Heniochus look delicate- they are not. They are indeed butterflies of the sea, who are hardy, undemanding and well-suited for aquaria.
Allen, Gerald R. and Roger C. Steene, 1978,79. Butterfly and Angelfishes of the World. Mergus, W. Germany
Burgess, Warren E., 1978 Butterflyfishes of the World. T.F.H. Publ., Inc. USA.
Debelius, Helmut 1981 (?), Wimplefish, the genus Heniochus. Aquarium Digest International #25
Goldstein, Robert J. 1971. Heniochus. Marine Aquarist 2(3):71.