The reef triggerfish, scientifically known as Rhinecanthus rectangulus, and affectionately called humuhumunukunukuāpua‘a in Hawaii, is a captivating and easily recognizable fish. Its unique appearance, combined with its intriguing behaviors, makes it a popular subject of interest for marine enthusiasts. One of the most crucial aspects of keeping a reef triggerfish healthy and thriving is understanding its dietary needs.
Identifying the Reef Triggerfish
The reef triggerfish is easily identifiable by its angular body, distinctive color pattern, and the characteristic dorsal spine. This sturdily built fish can reach up to 10 inches in length and possesses small, powerful jaws equipped with sharp, cutting teeth. Its unique method of swimming, using the waving motions of its dorsal and anal fins, allows for exceptional maneuverability, enabling it to move forward, backward, or even hover.
Natural Habitat and Feeding Habits
Reef triggerfish are commonly found in shallow outer reef habitats, particularly on surge-swept basalt reefs. They typically swim close to the bottom, actively searching for food. In their natural environment, their diet consists of algae and various reef invertebrates, including small crustaceans, worms, brittlestars, sea urchins, and snails. A dietary study on the rectangular triggerfish (Rhinecanthus rectangulus) revealed the following items in their stomachs (in order of importance): amphipods, tunicates, filamentous algae, crabs, polychaete worms, shrimps, coralline algae, snails, sea urchins, isopods, bryozoans, tiny clams, and crab larvae.
Feeding Reef Triggerfish in Captivity
In an aquarium setting, replicating the natural diet of a reef triggerfish is essential. They are not finicky eaters and have voracious appetites, requiring frequent meals to maintain their health.
Feeding Frequency and Quantity
One of the most important criteria for keeping healthy triggerfish is to feed them often-at least three and preferably five small meals a day. It is important to feed triggerfish several times a day, as they will rapidly lose weight if fed sparingly.
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Suitable Food Items
A varied diet is crucial for the well-being of reef triggerfish in captivity. Suitable food options include:
- Commercially available flakes and pellets: These provide a convenient and balanced source of nutrients.
- Freeze-dried food: This can be a good supplement to their diet.
- Frozen food: Mysis shrimp, krill, and brine shrimp are excellent choices.
- Live foods: These can provide enrichment and stimulate their natural hunting instincts.
- Hard-shelled shrimp and shellfish: These help to keep their teeth trimmed.
- Squid, fish, and clam: These offer meaty options that triggerfish enjoy.
- Nori: This seaweed can be a beneficial addition, especially when housed with a lawnmower blenny.
Tips for Feeding
- Thaw frozen food: Thaw frozen cubes of mysis, krill, or brine shrimp before feeding.
- Feed small portions: Squirt a small amount of food into the tank at a time, until the fish appears full.
- Remove uneaten food: Promptly remove any uneaten food to prevent water quality issues.
- Avoid overfeeding: Never offer more food than they can consume within one to two minutes.
- Garlic supplementation: Treating food with garlic can enhance the appetite of fish and encourage them to eat prepared foods.
Addressing a Skinny Triggerfish
If a reef triggerfish appears skinny or bony, it's essential to increase its food intake. Feed as much as it will eat, multiple times a day, until it appears full. Mysis, krill, brine shrimp, and carnivore pellets are all good options.
Potential Issues with Feeding
- Messy eaters: Reef triggerfish can be messy eaters, scattering food throughout the tank. To minimize this, cut the food into small pieces and feed in a controlled manner.
- Uneaten food: Uneaten food can decompose and negatively impact water quality. Promptly remove any uneaten food and consider using a filter system to maintain water quality.
Reef Compatibility
When considering keeping a reef triggerfish in a reef aquarium, it's essential to carefully consider its compatibility with other inhabitants. Triggerfish naturally nip at corals and invertebrates in their habitat. While some triggerfish species are more reef-safe than others, it's crucial to make informed decisions to prevent potential harm.
Reef-Safe Triggerfish
The best triggerfish for reef aquariums belong to the genera Melichthys, Odonus, and Xanthichthys. These species primarily feed on zooplankton or floating algae and are less likely to disturb corals and invertebrates.
Triggerfish to Avoid
More aggressive triggerfish species, such as the queen, gray, blue-lined, clown, and orange-lined triggerfish, are generally not suitable for reef aquariums. They may nip at corals and invertebrates, causing damage.
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Considerations for Keeping Triggerfish with Invertebrates
If you choose to keep a triggerfish with invertebrates, it's essential to select tankmates carefully. Soft corals with toxins may be unpalatable to triggerfish, reducing the risk of damage. Additionally, feeding the triggerfish frequently can help to minimize its interest in invertebrates.
General Care and Tank Requirements
Beyond diet, several other factors contribute to the health and well-being of reef triggerfish in captivity.
Tank Size
Triggerfish are active and territorial, requiring ample space to swim and explore. A minimum 55-gallon aquarium is recommended for a single juvenile triggerfish, while an adult needs at least 125 gallons.
Water Parameters
As saltwater species, triggerfish require specific water parameters to thrive. Maintain the water's specific gravity between 1.020 and 1.025, and the temperature between 72 and 78°F. Regularly test the water to ensure that pH, ammonia, nitrate, and nitrite levels are stable and within a safe range.
Filtration
A robust filter system is crucial for maintaining water quality in a triggerfish aquarium. Power filters and external canister filters are recommended because they offer effective mechanical, biological, and chemical filtration.
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Substrate
Line the bottom of the tank with at least 1-2 inches of substrate. Rinse the substrate with clean running water before adding it to the tank.
Tank Maintenance
Regular tank maintenance is essential for the health of triggerfish. Perform a full cleaning once a month, including cleaning the substrate, removing algae from the tank walls, rinsing filter media, and checking and replacing any necessary equipment.
Potential Health Issues
Although triggerfish are generally hardy, they can be susceptible to certain health issues.
Aggression
As triggerfish mature, they can become territorial and aggressive. Monitor the aquarium for fighting and other signs of aggression.
Jumping
Triggerfish are capable jumpers and may leap out of their tank when startled. Ensure that the tank is securely covered.
The Humuhumu as a State Symbol
In 1984, the reef triggerfish (Rhinecanthus rectangulus) was selected as the official State Fish of Hawai‘i, a testament to its cultural significance and popularity.
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