The pyramid butterflyfish (Hemitaurichthys spp.) are oddballs of the family Chaetodontidae. This fish specializes in feeding on zooplankton. The pyramid butterflyfish is usually found in shoals that swim high in the water column to pick off plankton prey. Because of its plankton-feeding proclivities, the pyramid butterflyfish is one of a handful of butterflyfish that is “reef-safe.” The most attractive member of the genus is the yellow pyramid butterflyfish (Hemitaurichthys polylepis).
Difficulty: The yellow pyramid butterflyfish is a moderately hardy aquarium fish. The yellow pyramid butterflyfish should be provided with plenty of space and fed frequently. You should provide frozen, shredded seafood, frozen carnivore preparations, frozen mysid shrimp and frozen fish eggs several times a day. If the yellow pyramid butterflyfish is not fed frequently, it will rapidly lose weight and may even resort to picking at corals, such as Anthelia or Xenia polyps, in the reef aquarium.
Physical description: The yellow pyramid butterflyfish is a deep-bodied fish with a brown head and a white body. The anal fin, the anterior portion of the body and dorsal fin, and a rear section of the dorsal are brilliant yellow. Hemitaurichthys polylepis reaches a length of 7 inches. The most similar species is the black pyramid butterflyfish (Hemitaurichthys zoster). The yellow pyramid butterflyfish is a resident of the Indian Ocean and has a dark brown head and posterior body, with a white section in between. The yellow pyramid butterflyfish also has a white tail. Its behavior and husbandry are similar to H. polylepis. There are two other species in this genus that are monochromatic gray or brown, which have little appeal to marine aquarists.
Range: The yellow pyramid butterflyfish is a resident of the eastern Indian Ocean (Christmas Island) east to the Hawaiian Islands in the Pacific. As with many zooplankton-feeding species, the yellow pyramid butterflyfish tends to frequent current-prone areas of exposed reef faces and slopes. The yellow pyramid butterflyfish often forms mixed groups with plankton-feeding damselfish, anthias and triggerfish. The yellow pyramid butterflyfish is found at depths of 10 to 150 feet. At night, the yellow pyramid butterflyfish hides in reef crevices.
Compatibility: The yellow pyramid butterflyfish is not aggressive to nonrelated fish species. The yellow pyramid butterflyfish may chase members of its own genus or other butterflyfish, but these encounters are rarely violent and tend not to result in injury to the attacked fish. That said, yellow pyramid butterflyfish may incessantly chase each other if they are crowded in a smaller aquarium. Subordinate fish may become intimidated by bossy conspecifics and stop feeding or may hide all the time. If this occurs, you will have to remove one of the H. polylepis to prevent the subordinate fish from wasting away. Pyramid butterflyfish are sometimes shagged by larger angelfish, more belligerent butterflyfish, surgeonfish and triggerfish. If the yellow pyramid butterflyfish is going to be housed with potential bullies, introduce the pyramid butterfly and fully acclimate it before the bullies are added. As mentioned, the yellow pyramid butterflyfish is the perfect butterflyfish for the reef aquarium, as it tends not to feed on any ornamental invertebrates. However, if the yellow pyramid butterflyfish is underfed, it may begin nibbling on large-polyped stony corals and soft corals, such as Anthelia and Xenia.
Aquarium conditions: The yellow pyramid butterflyfish needs a spacious aquarium home with plenty of swimming space. An aquarium of 100 gallons or more is preferred. Make sure you do not pack the aquarium with decor, so that the yellow pyramid butterflyfish can swim about without obstructions. The aquarium decor should be placed so that it has crevices and caves that the yellow pyramid butterflyfish can dash into when frightened. Keep the water parameters for the yellow pyramid butterflyfish as follows: pH of 8.1 to 8.4, specific gravity of 1.019 to 1.025 and a water temperature of 74 to 82.
Care considerations: At night or when stressed, the color of the yellow pyramid butterflyfish’s body will darken, and a white spot may appear on the side. This coloration should not be present when the lights are on if the yellow pyramid butterflyfish is “happy.”
Breeding: The yellow pyramid butterflyfish is not likely to spawn in the home aquarium.