The elegant pyramid butterflyfish (Hemitaurichthys polylepis) regularly appears in the aquarium trade, although the species is nearly impossible to breed in small tanks. They are not a particularly good species for beginners, as they need the utmost in water quality; but an experienced and dedicated hobbyist might find them delightful.
Pyramid butterflyfish belong to the class Actinopterygii, ray-finned bony fishes, as opposed to cartilaginous fish like sharks and a few lobe-finned fish. This is your typical fish group, the largest of all fish classes. Within this class, butterflyfish are in the order Perciformes -- perchlike fish, also a huge group -- and the family Chaetodontidae. Butterflyfish are colorful, sideways-flattened little fish. About 114 species of butterflyfish are known to science.
The pyramid butterflyfish is a naturally occurring species, not an artificial hybrid variety like so many aquarium fish. In fact, those found in home aquariums are exactly like those found in the wild because they were wild-caught in the first place. Fish appeared during the Cambrian period about 530 million years ago, although the two classes of bony fish didn't appear until the Ordovician, about 485 million to 443 million years ago. The evolution of coral reefs as we know them and the fish species associated with them didn't occur until much later.
Habitat and Ecology
The pyramid butterflyfish inhabits reef habitats in the central and western Pacific, including waters of Australia, Malaysia and Japan. Unlike most butterflyfish, which graze the corals of a reef, the pyramid butterflyfish feeds on plankton near the surface, adding to the species' appeal for aquariums -- the butterflyfish won’t demolish a reef tank. This is a social species, congregating in shoals around the edges of reefs.
The IUCN lists the species as of “least concern,” as it is currently plentiful and widespread. Potential threats include those affecting the butterflyfish food supply, such as climate change and ocean acidification. The aquarium trade poses little if any danger to this species, as numbers taken are fairly small in proportion to the population as a whole.
If you decide to keep pyramid butterflyfish, you’ll need a large reef tank to accommodate a small group. These fish won’t harm corals or other sessile invertebrates and are too big to become lunch for most other aquarium creatures. They might struggle to get enough food if the tank contains more assertive fish, though.
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