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Related FAQs: Rhinecanthus species, Rhinecanthus Triggers 2, Rhinecanthus Trigger ID, Rhinecanthus Trigger Behavior, Rhinecanthus Trigger Compatibility, Rhinecanthus Trigger Selection, Rhinecanthus Trigger Systems, Rhinecanthus Trigger Feeding, Rhinecanthus Trigger Disease, Rhinecanthus Trigger ReproductionTriggerfishes in General, Triggerfish: Identification, Selection, Selection 2, Compatibility, Behavior, Systems, Feeding, Diseases, Triggerfish Health 2

Related Articles: Triggerfishes (Family Balistidae), Red Sea Triggerfishes, Triggers of the Cook Islands

It’s the Humuhumunukunukuāpuaʻa, Lagoon, Picasso & More Triggerfish, Rhinecanthus aculeatus


Bob Fenner


Triggerfishes for  Marine Aquariums
Diversity, Selection & Care

New eBook on Amazon: Available here
New Print Book on Create Space: Available here

by Robert (Bob) Fenner

    Of the several Triggerfishes (Family Balistidae) employed by aquarists as erstwhile centerpieces; the genus Rhinecanthus members really stand out. Unlike the ever irascible and way too large Clown, Titan, Blunthead… Triggers they don’t get too big or mean; and on the positive traits side, they’re not as shy and reclusive as the popular “reef” Balistids of the genus Xanthichthys.

            Understanding this, Humu, Huma, Lagoon triggers, are definitely NOT for all systems. They do get of moderate size (about a foot maximum) and need good volumes (a couple hundred gallons plus) to feel comfortable enough to do well. Further, they’re not carte blanche compatible with every species you might want to co-stock. Balistids period will consume most all crustaceans, mollusks and worms; and “the” Picasso is no exception. It may well leave your corals alone, but even so, do keep in mind that this fish is rambunctious, a messy eater and copious waste producer.  

A one inch tiny specimen and a mid-sized four incher in captivity below right; and an eight inch adult out in Aitutaki, Cook Islands further down.


Distribution/Sources/Size: Indo- Pacific. Red Sea to Hawaii; even the eastern Atlantic! Not just reef-associated, but on, above, and in reefs in tropical shallow water a few feet to a couple hundred foot depths.

This species grows to a total of 30 cm., aka a foot in the wild. About half this in captivity.

And oh yes; this fish has quite a few other common names; and confusingly share some of these with other species of Balistids.


Selecting/Stocking/Compatibility: Picking out Humu Triggers is easy. This species handles collection, shipping and captive housing with ease. Even quite thin, obviously beaten specimens with frayed fins generally rally and repair given food and decent care.

            Though I’ve stated the penchant Triggers have for polyglot consumption, and warned re this one species possible coral chomping; let me re-state: This fish is NOT safe with actually any other species… IF it is hungry, bored, stressed… or just in the mood, it WILL sample most anything (including Seastars, Urchins…) it can get its small, but powerful jaws around. Best to procure a small/er one… place it last and have it grow up with your other livestock. There should only be ONE specimen per tank, and it’s better by far if this is the intended alpha fish.


System: As alluded to above, this Triggerfish needs SPACE; you may get away with cramping it into something of a few tens of gallons when it’s small, but it will suffer for being shoe-horned into too small a volume in time; psychologically… resulting in anomalous behavior; and a much shortened, unhappy life. A six foot long, one hundred fifty gallon system is the smallest I’d figure on for keeping this fish.

            This fish is constantly moving in the wild; sleeping tucked into rock-work by night to avoid predators like moray eels and sharks. It naturally occurs on reefs amongst rock/rubble, coral and sandy areas, and is happiest displayed with such in aquariums.

            Good brisk water movement, oversized filtration and regular water changes with gravel-vacuuming are de riguer in keeping systems containing Triggerfishes. Do provide some cave-like space in your hard-scape arrangement for your Trigger to get into and lie down during night time.


Foods/Feeding/Nutrition: This fish, actually all Triggers, is/are opportunistic omnivores; will consume algae, eggs and wastes of other animals, invertebrates of all kinds, other fishes. For aquarium maintenance it should be fed a mix of the above, including meaty foods daily, and incorporating occasional live or frozen/defrosted shellfish (crustacean and mollusc) in the shell, to help grind-down the fish’s ever-growing teeth.

            Twice, thrice daily feedings are better than less frequent.


Disease/Health: Triggers are generally tough, but can get and succumb to the usual environmental insults of poor water quality, a lack of nutrition, stress and pathogenic diseases. Happily, these fish are easy to diagnose for all the above; and IF there are biological agents at play, can withstand exposure to aquarist remedies.


Reproduction: A territorial species that “builds nests”, known to re-occupy about the same area for years. Both sexes are ferocious re guarding these spots… against all other fishes, most invertebrates, and divers! I have scars from many years back from bites from spawning Balistids. As you might presume, they are NOT bred in captivity; the space required being thousands, tens of thousands of gallons.

            Females (more than one per wandering male) guard the nest, laying eggs near sunrise, keeping the fertilized ova safe for about half a day, when they hatch and float/swim up to join the pelagic plankton; where they are broadcast by prevailing currents.


Cloze: The Hawaiian name for this, humuhumunukunukuāpuaʻa means “water pig with a needle”; refers to its eating habits, grunt-noise making at times and needle: a reference to the locking dorsal spines used to anchor the fish into a hole should a predator be about or currents too strong. Other than a fab Don Ho song; Rhinecanthus aculeatus can make a delightful centerpiece given a proper setting; fish only for sure; though I’ve seen the species kept in full-blown reefs. Do you have a space for such?


A nicely colored juvenile R. aculeatus in the Ari Atoll, Maldives



Triggerfishes for  Marine Aquariums
Diversity, Selection & Care

New eBook on Amazon: Available here
New Print Book on Create Space: Available here

by Robert (Bob) Fenner

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