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Big Longnose Butterflyfish


More delicate, difficult to feed species

Big Longnose Butterflyfish (Forcipiger longirostris)

Image by Keoki and Yuko Stender

Guide Fish Care Rating:

3 Stars

Family: Chaetodontidae.

Scientific Name: Forcipiger longirostris (Broussonet, 1782). Sometimes this fish is seen in a dark brownish-black color phase, which is is given the name F. inornatus (Randall, 1961), and therefore is a synonym of F. longirostris. F. cyrano (Randall, 1961) is also noted as a synonym.

Other Common Names: Forceps Fish.

Hawaiian Names: La-u wi-li-wi-li nu-ku-nu-ku 'o-i 'o-i, and La-u ha-u.

This rather uncommon Butterflyfish and its very common relative, the Yellow Longnose (Forcipiger flavissimus) have one of the longest Hawaiian fish names. Its meaning, leaf (lau) of the wili-wili tree with a long or sharp ('oi-'oi) nose (nu-ku nu-ku).


The Big Longnose species has a longer snout with a much smaller mouth at the end than its Yellow Longnose Butterflyfish counterpart. The two species can also be separated by counting their dorsal spines. This fish usually has 12 spines and from 25 to 28 soft rays, while the Yellow Longnose usually has 12 spines and from 22 to 24 soft rays. With some minor color differences on the head, the Big Longnose has a mid-dorsal band on the snout that is absent on the Yellow species.


Extends from Hawaii southeastward to the Tuamotu Islands and westward through Micronesia, Melanesia, and the East Indies.

Average Size: To about 9 inches.

Suggested Minimum Tank Size: 75 gallons.


The Big Longnose Butterflyfish is uncommonly seen, as it inhabits deeper waters on the outer side of the reef. It should be provided with plenty of shelter and room to move around. It is a fish that is sensitive to even the lowest levels of ammonia, as well as touchy to other changes in its environment relating to poor water quality issues.

Reef Tank Compatibility:

Unpredictable. Have been known to pick at stony and soft coral in the wild. It will eat fan or tubeworms and other desirable sessile invertebrates, as well as may pick at the tube feet of sea urchins.

Diet & Feeding:

This is a fish that can be more of a challenge when it comes to feeding because its tiny mouth limits the size of foods it can consume. Its diet consists primarily of living marine organisms, such as amphipods and copepods, and therefore it is best kept in a reef tank or fish-only aquarium that is partially filled with live rock that has an ample population of natural prey organisms present to feed on.
If this fish is not provided with an adequate and ample diet, it can easily starve in captivity. The Big Longnose Butterflyfish will accept typical aquarium Butterflyfish fares, but all foods offered need to be finely chopped up first.

Suggested Feedings:

At least 3 times a day.


Although the Big Longnose behaves in the typical Butterflyfish manor, it is a species that is best kept singly or in larger aquariums as a mated pair. It may fight with other Butterflyfish species, especially its Yellow Longnose relative. This fish does best when kept with other non-aggressive fishes, but can be placed into a moderately-aggressive community if introduced into the aquarium first.

Even though the "Fishes of Hawaii" book states that the dark color phase is characteristic of juveniles, we have collected these fish in the dark color phase at adult size. When captured and placed into an aquarium they loose their dark color and revert back to having yellow bodies. It is a gradual change that can take many weeks to reach completion. As the dark color fades the fish begins to take on a blotchy yellowish-brown appearance, and as time progresses it slowly, but eventurally becomes yellow again. Needless to say it can be a pretty ugly looking fish during this transformation.

Guide Fish Care Rating: 3 Stars

>> Read more Butterflyfish Species Profiles

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