Smalltail Pencil Wrasse

The Smalltail Pencil Wrasse, Pseudojuloides cerasinus, is a slender, exceptionally colorful marine wrasse prized for its elegant shape and constantly active foraging behavior. Terminal-phase males display brilliant green coloration accented by vivid blue and yellow horizontal striping, often with a darkened rear portion of the tail. Females and initial-phase individuals look dramatically different, displaying pink, salmon, or reddish coloration before potentially transitioning into the striking green male form.

Native to the Hawaiian Islands, this species inhabits coral and rubble reef environments where it spends much of the day moving rapidly over the substrate in search of tiny benthic invertebrates. Its streamlined profile, intense adult male coloration, and energetic swimming style make it an impressive addition to a mature reef aquarium.

Despite its relatively small adult size, the Smalltail Pencil Wrasse is best suited to experienced aquarists. Members of Pseudojuloides can be sensitive during transport and acclimation, require frequent access to appropriately sized foods, and depend on a soft sand bed for sleeping and emergency shelter. A mature, food-rich aquarium with peaceful tankmates provides the best environment for long-term success.

Quick Care Guide

Care Level: Expert Only
Minimum Tank Size: 75 gallons
Temperament: Peaceful
Diet: Carnivore / Micro-predator
Reef Safe: With Caution
Region: Hawaiian Islands
Scientific Name: Pseudojuloides cerasinus

Tank Requirements

Provide a mature aquarium with abundant live rock, open swimming areas, and a well-established population of natural microfauna. Although relatively small, the Smalltail Pencil Wrasse is an active swimmer that continuously travels across the reef structure while searching for food.

A bed of fine, soft sand approximately 2–3 inches deep or greater is essential. This species dives beneath the substrate to sleep and will also bury itself rapidly when frightened. Coarse gravel, crushed coral, and sharp substrates should be avoided because they can injure the fish during this natural behavior.

Rockwork should provide numerous crevices and sheltered areas while still leaving substantial unobstructed swimming space. A mature reef with copepods and amphipods available throughout the day is especially valuable during acclimation.

A tightly fitted mesh or solid lid is mandatory. Pencil wrasses are exceptionally capable jumpers and may launch from the aquarium when startled, particularly during their first weeks in a new system.

Diet and Feeding

The Smalltail Pencil Wrasse is a carnivorous micro-predator that naturally searches reef rubble and substrate for tiny crustaceans and other benthic invertebrates.

Offer a varied diet consisting of mysis shrimp, enriched brine shrimp, copepods, Cyclops, finely chopped krill, small frozen plankton blends, and other appropriately sized marine foods. High-quality micro-pellets may be accepted once the fish becomes established, but prepared dry foods should not be relied upon during initial acclimation.

New specimens can be hesitant feeders. Live copepods, live enriched brine shrimp, or live mysis can be useful for stimulating a feeding response before gradually transitioning the fish onto frozen preparations.

Feed at least two to three small meals daily, with additional small feedings beneficial when practical. A mature aquarium containing abundant natural microfauna allows the wrasse to forage between scheduled meals and can significantly improve long-term condition.

Temperament and Tankmates

The Smalltail Pencil Wrasse is generally peaceful toward unrelated fish and should be housed with calm, non-aggressive tankmates. Suitable companions include peaceful clownfish, gobies, blennies, cardinalfish, anthias, fairy wrasses, flasher wrasses, and other relatively gentle reef species.

Avoid aggressive wrasses, territorial damsels, large dottybacks, aggressive triggerfish, groupers, and other fish likely to intimidate or outcompete it. Stress from aggressive tankmates can cause a pencil wrasse to remain buried, refuse food, or repeatedly attempt to escape.

Males may become territorial toward other male pencil wrasses or closely related species. Females may transition into terminal-phase males when no dominant male is present, accompanied by a dramatic change in coloration.

For most aquariums, a single specimen is the simplest arrangement. Carefully selected pairs or groups require considerably more space and close attention to social dynamics.

Reef Compatibility

The Smalltail Pencil Wrasse is generally coral-safe and does not normally consume SPS, LPS, or soft coral tissue.

It is best classified as reef safe with caution, however, because small crustaceans and other tiny benthic invertebrates form part of its natural diet. Very small shrimp, tiny crabs, worms, amphipods, copepods, and similar organisms may be hunted.

Established corals and larger ornamental invertebrates are generally less concerning, making this species suitable for many mature reef aquariums when some predation on microfauna is acceptable.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Stable temperature, salinity, oxygenation, and overall water quality are particularly important for this sensitive wrasse. Consistency should be prioritized over chasing exact numbers within these ranges.

Common Considerations

• A mature aquarium with abundant copepods, amphipods, and other natural microfauna is strongly recommended.

• A fine sand bed is essential because the fish buries itself every night and whenever frightened.

• Acclimation and feeding can be challenging, making this species better suited to experienced marine aquarists.

• A tightly fitted lid is mandatory because pencil wrasses are powerful jumpers.

• Females and initial-phase fish may eventually transition into dramatically different green terminal-phase males.