Squareback Anthias - Male - Fiji
Squareback Anthias - Male - Fiji
Goes well with:
FAQs Answers to the most common questions.
Is Pink Square Anthias best kept as a single fish, or does it need a group?
It is much better kept in a small harem or group, not alone. Like most anthias, the most stable setup is one dominant male with 3–6 females. A lone Pink Square Anthias often becomes timid, refuses food, or fades in color. If kept in a pair, make sure one is clearly male and the other is female; two similar-sized individuals may fight.
What foods reliably get Pink Square Anthias feeding in captivity?
They usually do best on frequent small feedings of meaty planktonic foods: enriched mysis, copepods, baby brine shrimp, finely chopped krill, and high-quality marine pellets designed for planktivores. The key is variety and frequency. Offer food 2–4 times daily if possible. Newly imported fish often start with live or frozen copepods and baby brine shrimp before accepting pellets.
How can I tell if a Pink Square Anthias is male or female?
Males are typically more intensely colored, more assertive, and often show more elongated dorsal, anal, or caudal fin extensions depending on the individual. Females are usually smaller, rounder in profile, and less vivid. In a group, the largest, most dominant individual often transitions into male if no male is present.
What tank setup suits Pink Square Anthias best long-term?
They do best in a mature reef-style aquarium with strong water movement, high oxygenation, and plenty of open swimming space plus some sheltered rockwork. Stability matters more than minimalism: low nitrate, no sudden salinity swings, and excellent filtration are important because they are sensitive to poor water quality. A tight-fitting lid is also important, since anthias are jumpers.
Why do Pink Square Anthias sometimes waste away even when they seem to be eating?
This is a common anthias problem and usually comes from not feeding often enough, foods being too large or too rich, or the fish being outcompeted at meals. They burn energy quickly and need frequent access to small, nutrient-dense foods. Another issue is internal parasites or shipping stress, especially in newly imported specimens. If one is eating less, isolate it if needed, increase feed frequency, and watch closely for rapid weight loss behind the head and belly.
All listed sizes are approximate, not guaranteed, and may vary slightly.
The male Squareback Anthias (Pseudanthias pleurotaenia), also known as the Squarespot Anthias, Square-Spot Fairy Basslet, or Purple Blotch Anthias, is a spectacular saltwater fish recognized for its vivid pink, reddish-orange, and magenta coloration. Mature males typically develop a large pale lavender-to-whitish quadrangular patch on the side of the body, along with blue-edged fins, an elongated dorsal spine, and a deeply forked tail. The size and intensity of the characteristic flank patch can vary between individuals and geographic populations.
This Fiji-origin form comes from the South Pacific portion of the species’ range, where Squareback Anthias inhabit current-swept reef slopes and drop-offs. In nature, they form aggregations several feet above reef structure, remaining in the water column to capture passing zooplankton while retreating quickly toward the reef when threatened.
Reaching approximately 8 inches as an adult, the male Squareback Anthias is substantially larger than many commonly maintained anthias and requires generous swimming space. Its dramatic coloration, active behavior, and coral-safe feeding habits make it an impressive centerpiece for a spacious reef aquarium or appropriately sized fish-only aquarium.
Quick Care Guide
Care Level: Moderate
Minimum Tank Size: 125 gallons
Temperament: Semi-aggressive
Diet: Carnivore / Planktivore
Reef Safe: Yes
Region: Fiji – South Pacific
Scientific Name: Pseudanthias pleurotaenia
Tank Requirements
Provide a mature, well-established marine aquarium with extensive open swimming space above and around the rockwork. Male Squareback Anthias are large, active water-column swimmers, so a long aquarium footprint with substantial unobstructed swimming room is preferable for long-term housing.
Arrange live rock to provide caves, ledges, overhangs, and shaded retreats without excessively reducing open water. Secure retreats are important for nighttime shelter and allow the fish to withdraw from aggressive interactions or bright aquarium lighting when desired.
Moderate to strong, well-distributed water movement is ideal and helps replicate the current-swept reef habitats where this species naturally feeds. Strong oxygenation and efficient filtration are especially important because frequent feeding can contribute significant nutrient input.
A securely fitted mesh screen or aquarium lid is recommended, as anthias may jump when startled or chased.
Diet and Feeding
The Squareback Anthias is a carnivorous planktivore that naturally feeds on zooplankton and small crustaceans suspended in the water column.
Offer a varied diet including enriched mysis shrimp, enriched brine shrimp, copepods, calanus, frozen plankton blends, finely chopped marine seafood, and appropriately sized high-quality marine pellets or flakes. Foods that remain suspended in the water column help encourage natural feeding behavior.
Provide two to three small meals per day, with additional smaller feedings beneficial when practical. Newly introduced specimens may initially respond most readily to mysis shrimp, copepods, and other frozen planktonic foods before becoming accustomed to a broader prepared diet.
Temperament and Tankmates
Male Squareback Anthias are generally compatible with peaceful to moderately assertive marine fish but can become territorial toward other anthias. Mature males may display, chase females, or aggressively challenge competing males as they establish and maintain social dominance.
Suitable tankmates include tangs, rabbitfish, peaceful to moderately assertive angelfish, fairy and flasher wrasses, clownfish, gobies, and other non-predatory marine species that will not continually intimidate or outcompete them.
Multiple mature males should generally be avoided unless the aquarium is exceptionally large and provides substantial separation between territories. A single male can be maintained successfully, or one male may be housed with several females in a suitably spacious system.
Like other anthias, this species is a protogynous hermaphrodite. If a dominant male is absent, a dominant female may transition into a male as the social structure of the group changes.
Reef Compatibility
The male Squareback Anthias is considered reef safe and is an excellent choice for large coral-dominated aquariums. It does not normally consume or damage stony corals, soft corals, clams, or other sessile reef organisms.
It is also generally compatible with ornamental shrimp, crabs, snails, and other established reef invertebrates. Tiny copepods and other planktonic crustaceans will naturally be consumed as part of its normal feeding behavior.
Water Parameters
Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH
Maintain stable, highly oxygenated water with consistently good water quality. Efficient filtration and regular nutrient management are particularly important because this active anthias benefits from multiple daily feedings. Stability is more important than targeting one exact value within these ranges.
Common Considerations
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Large adult size: Can reach approximately 8 inches and requires substantial open swimming space.
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Male coloration: Mature males typically develop vivid pink-to-magenta coloration with a prominent pale square or rectangular flank patch.
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Male territoriality: May aggressively challenge other male anthias and chase subordinate individuals.
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Frequent feeding: Benefits from several small meals of plankton-sized, protein-rich marine foods throughout the day.
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Active reef swimmer: Requires strong oxygenation, open water, secure retreats, and a mature aquarium environment.
