There are at least two species of Bannerfish that are ornamentals in the
marine aquarium trade:
Heniochus diphreutes which is a planktonivore and
Heniochus acuminatus which is a coralivore/omnivore. The morphological difference is very slight between the two, but discernable at the anal fin in particular and the shape of the snout.
The black edging on the
H. acuminatus anal fin is absent on the
H. dipheuretes, a few other small differences (like the number of rays in the dorsal fin, etc. ) but the main difference is the schooling bannerfish (
H. dipheuretes) is a plantkon feeder, and will pick the zooplankton from the water column with relish (and is much easier to get to eat) wheras the Pendent Coralfish (
H. acuminatus) is a polyp feeder, and although it will eat flake, zooplankton, etc, it will also consume polyps whenever given the opportunity, or when other food stuffs are not plentiful. The snout of the
H. diphreutes specie is more angular to the overall shape of the facial plane, as if it had an endented notch in the middle of its forehead. The
H. acuminatus is a more straight face, as if it were a "V" formed from above the area above the forehead to the opiculum, with the oral opening at the peak of the "V". IME the larger the
H. acuminatus specimen is when brought in from the wild (and subsequently the more experience it has had with eating in the wild), the more likely it is to consume polyps. I have seen what the
H. acuminatus will do to polyps...
H. dipheuretes are quite the beautiful fish, and very personable. Mine would take zooplankton out of my hand, with the "banner" dorsal fin breaking the surface of the water (Mel thinks it is related to the shark-attack-behavior of the fish when feeding the thawed zooplankton
). I (unfortunately in terms of keeping these little beauties) made the decision to stay away from schools of fish to concentrate on
stony corals (fewer fish = less nutrient load in the tank = better stony coral coloration), but if you have a large tank and don't concentrate on stony corals, these are great fishes for schooling as the butterflies of your coral garden.
see
Schooling bannerfish species summary
and
Pennant coralfish species summary
HTH
