Rhino Leatherjacket Filefish

The Rhino Leatherjacket Filefish (Pseudalutarius nasicornis), also called the Rhinoceros Leatherjacket or Rhino Filefish, has a narrow cream to gray-brown body with two darker lines along its upper sides. A dark mark on the rounded tail may be bordered by a pale ring. Its most distinctive feature is the long first dorsal spine, which rises well in front of the eyes and gives the fish its name. Adults may show small yellow spots on the head and body.

This species occurs across the Indo-West Pacific, from southern Africa through Indonesia and north to southern Japan, with records along eastern Australia. It inhabits coastal reefs, sandy and weedy areas around lagoons, and rubble slopes with abundant invertebrate growth. Small individuals have been observed taking shelter around sea whips and sea pens. Its slim outline and slow movements help it blend in near upright cover.

In the aquarium, the Rhino Leatherjacket tends to hover and make short, deliberate feeding movements around structure. A mature display with calm tankmates gives it time to investigate food and retreat when startled. Set up the permanent aquarium for a fish that can reach 7.5 inches, and consider the risk of browsing before keeping it with ornamental invertebrates.

Quick Care Guide

Care Level: Moderate
Minimum Tank Size: 55 gallons
Adult Size: Up to 7.5 inches (19 cm total length)
Temperament: Peaceful
Diet: Omnivore
Reef Safe: With Caution
Region: Indo-West Pacific, including southern Japan and eastern Australia
Scientific Name: Pseudalutarius nasicornis

Tank Requirements

Provide at least 55 gallons for long-term adult housing. The species can reach about 7.5 inches (19 cm) in total length, so choose a footprint with enough width to turn easily between rock structures. A larger, wider aquarium is preferable when the rockwork occupies much of the tank or other fish use the same swimming and feeding areas.

Arrange stable rockwork with shaded recesses, a few upright structures, and clear gaps where the fish can hover. Leave space around the cover so the adult can turn without brushing against it. A shallow sand bed or an open patch beside rubble can give the fish another area to investigate. Arrange the rock and sand so settled food can be seen and removed.

Provide a sheltered feeding lane. Distribute circulation so a gentle current carries food past a ledge or upright structure. Keep a quieter area where the fish can hover without swimming continually. Maintain surface movement and oxygenation in the rest of the display.

Set up several routes between shelter and open water before introducing the fish. A newly arrived filefish may choose a low corner or a ledge different from the one planned. Feed near the cover it actually uses and keep a second refuge available in case another fish occupies the first.

Use a fully established biological filter and a securely fitted cover. Keep access around the rocks for siphoning and clean mechanical filtration after food begins to collect. A mature system with stable water and predictable feeding is particularly useful when the fish is first adjusting to prepared foods.

Diet and Feeding

Offer a varied omnivore diet with small marine animal foods as the main component and algae-based foods in the rotation. Use small portions that suit the fish’s narrow mouth. Prepared frozen foods and appropriately sized pellets or flakes can be offered once the fish is taking food reliably.

Rotate suitable foods from these options.

• Small frozen mysis shrimp
• Enriched brine shrimp
• Finely chopped marine shrimp, clam, or other seafood
• Balanced frozen marine omnivore preparations
• Fine marine pellets or flakes once accepted
• Small portions of marine algae or spirulina-based foods

Start with two or three small meals a day and adjust to appetite, body condition, and the amount of food left over. Deliver the first portion where the fish usually hovers. In a community aquarium, feed active tankmates at a separate point so the filefish has time to approach and take several bites.

Watch for swallowing. A filefish can inspect food or take it into its mouth without eating much. If the fish repeatedly spits out food, offer finer pieces and try small frozen foods before increasing the portion. Enriched live prey can help start a feeding response in a reluctant new arrival.

Introduce complete prepared foods gradually and retain several options the individual takes consistently. Remove uneaten seafood and algae before they break down. Use several feeding observations to judge condition, particularly when the fish spends much of the day near shelter.

Temperament and Tankmates

The Rhino Leatherjacket is generally peaceful with unrelated fish. Its deliberate swimming and feeding make it a poor match for persistent fin nippers, territorial fish that patrol its shelter, or very fast feeders. Choose calm companions that allow it to come out and feed without repeated disturbance.

One specimen is the simplest choice for a typical display. Pairs are seen in the wild, but keep compatible fish together only when there is enough room for separate cover and feeding access. Watch how individuals use shelter after introductions and be prepared to separate fish if one is consistently displaced.

Watch for repeated chasing, damaged fins, or a fish that disappears through several meals. Provide an alternate retreat and a separate feeding position. Give new fish time to settle before adding bolder tankmates, and observe how the group behaves during feeding as well as at rest.

Reef Compatibility

The Rhino Leatherjacket is Reef Safe Caution. Its browsing can put coral polyps, clam mantles, and other small exposed invertebrates at risk. Individual behavior varies, and a fish that eats prepared food can still investigate living surfaces.

If kept in a reef, observe the colonies and invertebrates near the fish’s favored cover for repeated nipping or persistent retraction. A fish-only aquarium with live rock offers the most predictable setup when the display contains vulnerable ornamental invertebrates.

Water Parameters

Temperature: 74–78°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Maintain a fully cycled, well-oxygenated marine aquarium with undetectable ammonia and nitrite. Replace evaporated water with fresh water and match the temperature and salinity of new saltwater during water changes. Verify that flow through the sheltered areas remains steady after filter or pump maintenance.

Track nutrient levels as feeding becomes more frequent. Siphon scraps from accessible areas and clean mechanical media before trapped food breaks down. Regular observation of appetite, breathing, and shelter use helps distinguish normal quiet behavior from a change that needs attention.

Common Considerations

• Adult Housing: Use at least 55 gallons with enough width for a 7.5-inch adult to maneuver around cover.
• Identification: Look for the first dorsal spine well ahead of the eyes, two darker upper body stripes, and a marked tail.
• Feeding Access: Place fine foods near shelter and verify that the fish swallows them before offering more.
• Tankmates: Choose calm fish that leave the filefish time to feed and access to cover.
• Reef Caution: Watch for browsing on coral polyps, clam mantles, and exposed invertebrates.
• Handling: Use a suitable rigid container where practical, as the dorsal spine can snag in fine mesh.