Threadfin Butterflyfish or Chaetodon auriga belong to the family Chaetodontidae which is comprised of 120 species in 10 different genera. This family is more commonly referred to as butterflyfish. This species is native to the indo-Pacific. Populations can be found throughout the Red Sea, as far north as Japan down the entire length of East Africa to as far south of Lord Howe Island situated southeast of Australia. Its natural habitat also extends from the Red Sea to the Hawaiian Islands. These fish occupy depths from surface level to approximately 100 feet.This is by far one of the most exotic butterflyfish marketed by the aquarium trade. It has a white, slightly elongated snout with a black vertical bar from its eyes to the bottom of its head. Its predominantly white body is striated with a pattern of ascending and descending oblique grey lines. This white and grey patterning darkens to a grey or black on yellow on the upper part of its posterior. Dorsal, anal and caudal fins are bright yellow. As it matures, this species develops a trailing filament on the back of its dorsal fin that extends passed it tail fin. This long tread-like extension is why they are called threadfins. This species frequently has an eyespot on the back of its dorsal fin. This false eye is not generally present on specimens from the Red Sea. In Hawaii this fish is called Kapuhili. It is often sold under the names Auriga Butterflyfish, and Cross-Stripe Butterflyfish.This is one of the best all around choices among butterflyfish for a community tank. It is hardier than most butterflies and comes with an easy care rating. Many butterflyfish are recommended for only expert level aquarists. This species can be raised by more novice hobbyists. Threadfins grow can grow up to 9 inches in length as adults and require a minimum tank size of 75 gallons. This species makes a wonderful addition to fish-only tanks but is not suitable for marine reef aquariums.

Most butterfly species are classified in the semi aggressive category. This particular species is of a more docile nature. They are quite shy for butterflyfish and will require plenty of hiding places. They will however display aggressive behavior toward conspefics (members of their own species) and fish of similar color pattern. Multiples can be kept in larger aquariums if introduced simultaneously, preferably as juveniles. A male-female couple will often forage for food separately and then perform a greeting display upon reuniting. They will spend most of their time swimming in close proximity of one another. The threadfin’s easy care rating and mild mannered temperament has made them one of the most popular butterflies in home aquariums.This is an omnivorous species. In its natural habitat its diet includes; sessile invertebraes, most large polyp stony coral polyps, feather dusters and fanworms and algae.In an aquarium it should be provided with plenty of live rock to graze on. In exchange it will perform the service of ridding your live rock of aiptasia anemones. Most aquarists consider this species a pest. They are quite frequently accidentally introduced to an aquarium with the addition of live rock. Once present they are notoriously hard to get rid of. If your aquarium suffers from aiptasia infestation you should consider purchasing a threadfin.These fish are not picky eaters. They will readily accept common variety food fare. They will also consume food preparations not intended for them. This is fine as long as their total consumption is a well balanced combination of plant, animal and algae matter. Dried algae sheets, chopped broccoli and asparagus are good supplements.As with most butterflyfish, this species is a sequential hermaphrodite. The introduction of two juveniles into an aquarium will result in a male-female pair. This fish seldom breeds in captivity.