Rectangle Triggerfish (Rhinecanthus rectangulus) known to tropical fish keeping enthusiasts as the Reef Triggerfish, Patchy Triggerfish, Rectangular Triggerfish, Wedge Picassofish, Wedge Tailed Trigger, or V-line Humuhumunukunukuapuaa, is found throughout the Indo West and Central Pacafic, and is the state fish of Hawaii.

The Humu Rectangle Triggerfish range extends from the Red Sea south to East London, South Africa and east through Indonesia to the Marquesan Islands and northern Australia up to Hawaii and Pitcairn islands, north to southern Japan, and south to Lord Howe Island.

Humu Rectangle Triggerfish are benthopelagic, generally solitary, and extremely territorial.

Adult Humu Rectangle Triggerfish are commonly found over barren rock as well as mixtures of bare rock, rubble, and coral situated along the shallow outer reefs and lagoons of their range which are subject to surges, at depths to 70 feet where they are often seen feeding on algae, detritus, echinoderms, mollusks, crustaceans, worms, fishes, sponges, foraminifera, and fish eggs.

Juvenile Rhinecanthus rectangulus are more commonly found on shallower algae reef roofs.

Humu Rectangle Triggerfish (Rhinecanthus rectangulus)

Humu Rectangle Triggerfish have an orange brown body color with a white head and belly; a pearly white face with two blue and black stripes across the eyes, a blue bar across the upper lip, a diagonal black V shaped band outlined in yellow that runs from the eye to the anal fin, and a black wedge shaped mark, preceded by two yellow V shaped marks on the caudal peduncle. The soft dorsal, anal, and pecroal fins are a pale dusky color. In juveniles, the yellow V shaped marks on the caudal peduncle are white.

Like Niger Triggerfish, adult and juvenile Rhinecanthus rectangulus have the ability to rapidly alter their coloration when sleeping or changing their moods. Their colors are most vivid when healthy and unthreatened but become drab in appearance when sleeping or demonstrating submission.

Humu Rectangle Triggerfish are not reef safe and do best housed in mature FOWLR tank of at least 180 gallon capacity with a sand or coralline gravel substrate, substantial amounts of live rock formed into caves, crevices, and overhangs for them to hide among, and plenty of free swimming space. A good filtration system, protein skimmer and wave maker to replicate the moderate to strong currents in their natural habitat is recommended.

Rhinecanthus rectangulus are pretty aggressive and generally will not tolerate conspecific individuals in their general vicinity. They do best with other larger semi aggressive species and should never be housed with smaller peaceful or docile species.

Although some tropical fish keeping enthusiasts have had success keeping Humu Rectangle Triggerfish in very large reef tanks without crustaceans and invertebrates, they constantly rearrange rocks and corals as they search for benthic invertebrates under the substrate, sifting and spitting sand over their surroundings.

Humu Rectangle Triggerfish are difficult to sex and have not been bred in an aquarium environment.

In their natural environment, Reef Triggerfish are omnivores that have a diverse diet.

They feed on algae, detritus, crustaceans like crab, shrimp, and lobster; mollusks like octopus and squid; worms and planktonic organisms, and smaller fish like sardines and anchovies.

In an aquarium environment, they require a varied diet of high quality marine pellets; live, fresh, or frozen squid, krill, clams, mussels, shrimp, Mysis, octopus, snails, scallops, and especially hard shelled shrimp to help wear down their teeth. Feeding small portions several times a day is recommended to a single large feeding.

Humu Rectangle Triggerfish (Rhinecanthus rectangulus) are available to tropical fish keeping enthusiasts from a variety of online suppliers and specialty fish shops at prices that vary according to size and area of collection.

Approximate purchase sizes: Small: 1″ to 2″; Medium: 2″ to 3-1/2″; Large: 3-1/2″ to 5″; X Large: 5″ to 6″; XX Large: 6″ to 8″.

Prices for small specimens start at around $49.99 for Sumatran specimens and increase to over $125.99 for large specimens.

Humu Rectangle Triggerfish (Rhinecanthus rectangulus)

Minimum Tank Size: 180 gallons
Aquarium Type: FOLR
Care Level: Easy to Moderate
Temperament: Semi Aggressive
Aquarium Hardiness: Hardy
Water Conditions: 72-78° F, dKH 8 – 12°, pH 8.1 – 8.4, sg 1.020-1.025
Max size: 12″
Color Form: Black, Blue, Orange, White, Yellow
Diet: Carnivore
Compatibility: Not reef safe
Origin: Indo West and Central Pacific
Family: Balistidae
Lifespan: Over 15 years
Aquarist Experience Level: Intermediate