Humu Rectangle Triggerfish saltwater fish care guide

The Humu Rectangle Triggerfish (Rhinecanthus rectangulus) is a stout, laterally compressed Indo-Pacific species built for life among surge-swept rock. The face and underside are pale, nearly pearly white, while the upper body carries a brownish-orange wash broken by blue-and-black facial bands, a broad dark diagonal band across the flank, and a prominent black wedge near the tail. Like other triggerfishes, it carries a heavy first dorsal spine that locks upright once the fish wedges itself into a crevice, an anchoring trick that makes it nearly impossible to extract from the reef. Reported maximum length is roughly 12 inches, with many aquarium and public-aquarium accounts describing adults closer to 10 inches.

Adults belong in a large fish-only or fish-only-with-live-rock aquarium of at least 180 gallons, combining wide-open swimming lanes with heavy rockwork, caves, and tight crevices for refuge and sleeping. Published minimums for this species range from 100 to 180 gallons, and the larger figure is the sensible target for a fish that reaches a foot and patrols constantly. Build the aquascape to stay put: this trigger rearranges rock, excavates the sandbed, and sifts substrate while hunting. In nature it occupies shallow outer reef zones over bare rock, rubble, and coral where wave surge is a constant, so a rugged, securely stacked layout suits it far better than delicate decor.

Wild specimens feed opportunistically on algae, detritus, mollusks, crustaceans, worms, echinoderms, sponges, eggs, and small fishes, which is why this species is best treated as an omnivore rather than a strict meat eater. In the aquarium it accepts chopped marine fish flesh, squid, krill, mysis or brine shrimp, clam flesh, and frozen meaty preparations, with some Spirulina or other algal material worked into the rotation. Offering hard-shelled shrimp and similar shelled items is more than enrichment: the continually growing teeth of a triggerfish need abrasive material to stay properly worn down.

Two or three smaller feedings spread through the day suit its active, food-searching habits better than a single large meal. Variety matters here, since a monotonous diet of soft frozen foods leaves the dentition unchecked and narrows nutritional intake. Most individuals feed readily and show no particular reluctance at the outset, so the practical concern is portion control and menu rotation rather than coaxing a hesitant eater.

Chopped Marine Fish Squid Krill Mysis Shrimp Clam Flesh Hard-Shelled Shrimp Frozen Meaty Preparations Spirulina
This is a diurnal, muscular, and decidedly aggressive fish that spends much of the day cruising and probing the rockwork for food. It is normally solitary and territorial, and aggression tends to intensify as the fish matures. Smaller tankmates are treated as prey, and the fish will grunt or vocalize when agitated. It is also bold enough to bite the hand of an aquarist working in the tank, so use tools rather than fingers during maintenance.

Suitable companions are comparably sized or larger, assertive fishes capable of holding their own, such as large moray eels, snappers, angelfishes, and tangs. Timid or peaceful species are poor choices, and slow-moving lionfishes are likely to have their fins nipped. Plan on one triggerfish per system unless the aquarium is exceptionally large and all individuals are introduced at the same time. This species is not reef safe: it nips corals and readily consumes ornamental shrimp, crabs, snails, urchins, and other mobile invertebrates, and safety for clams and other sessile invertebrates cannot be assumed. A fish-only or FOWLR aquarium is the appropriate long-term home.

FAQ

Frequently Asked Questions

About the Humu Rectangle Triggerfish

  • What size aquarium should I plan for?
    Published minimums for this species range from 100 to 180 gallons. A 180-gallon or larger fish-only system is the conservative long-term choice for a trigger approaching 12 inches.
  • Can a Humu Rectangle Triggerfish live in a reef aquarium?
    No. It nips corals and preys on crustaceans, mollusks, snails, and echinoderms, making a fish-only or fish-only-with-live-rock setup the correct home.
  • Which tankmates are appropriate?
    Choose comparably sized or larger, robust fishes such as large moray eels, snappers, angelfishes, and tangs. Avoid small, timid, or peaceful species and slow-moving lionfishes, and keep only one triggerfish unless the system is exceptionally large.