FishMarineIntermediate
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Squarespot Anthias
Pseudanthias pleurotaenia
One of the largest and most iconic Anthias species, with males instantly identifiable by a prominent square purple spot on their flanks.
Water Temperature
22 - 27 °C
pH Value
8.1 - 8.4
Water type
Marine
Tank level
All levels
Adult size
20 cm
Minimum tank volume
>= 500 L
Minimum group
>= 4
GH
15 - 25 dGH
KH
8 - 12 dKH
Species description
Geographical Origin and Habitat: Found in the Indo-West Pacific, from Indonesia and the Philippines to Samoa, north to southern Japan (Ryukyu Islands), and south to the Great Barrier Reef. Inhabits outer reef slopes and drop-offs at depths of 10 to 180 meters.
Taxonomy and Morphology: Member of the family Serranidae, subfamily Anthiadinae. It is one of the larger anthias species, reaching up to 20 cm in total length. Features a compressed, robust body with a deeply forked caudal fin.
Social Behavior: Lives in structured harems containing one dominant male and a group of females. Males defend their territory and harem from competing males. They swim in open water above the reef slopes.
Coloration and Sexual Dimorphism: Sexual dimorphism is highly pronounced. Males are bright pink-magenta with a distinctive purple-lilac square spot on their sides and blue-trimmed fins. Females are overall bright orange-yellow with violet lines running from the eye to the pectoral fins.
Care, breeding and tankmates
Aquarium Setup: Requires a spacious aquarium of at least 500 liters for a small harem. High water movement and excellent filtration are essential to handle organic wastes. Provide caves, overhangs, and shaded spots within the rockwork.
Diet and Feeding: Strictly zooplanktivorous. In captivity, must be fed 3 to 4 times daily with high-quality frozen foods like mysis, brine shrimp, calanus, and lobster eggs. They may be hesitant to accept dry food initially.
Water Quality: Demands pristine, highly oxygenated water. Temperature 22-27°C, pH 8.1-8.4, salinity SG 1.020-1.026. GH 15-25. A heavy-duty protein skimmer is vital to manage the high bioload from frequent feedings.
Compatibility and Cohabitation: 100% reef safe. Peaceful towards other non-conspecific reef fish. Avoid housing with overly aggressive species like dominant large surgeonfishes, which may intimidate them during feeding.
Aquarium Breeding: Extremely rare in captivity. They are protogynous hermaphrodites: if the male dies or is removed, the dominant female will transition into a male within a few weeks.
Risks and Diseases: The main threat is starvation due to inadequate feeding frequency. High stress during acclimation can make them susceptible to marine ich. A tight-fitting lid is mandatory as they are notorious jumpers.
Geographic Origin and Distribution
Found in the Indo-West Pacific, from Indonesia and the Philippines to Samoa, north to southern Japan (Ryukyu Islands), and south to the Great Barrier Reef. Inhabits outer reef slopes and drop-offs at depths of 10 to 180 meters.
Origin
Tropical oceans and reefsSouth and Southeast AsiaEast Asia
Fish profile
- Temperament
- Semi-aggressive
- The temperament of Pseudanthias pleurotaenia is generally peaceful towards completely unrelated fish, making them wonderful community residents. However, they establish a strict pecking order within their own group, which can involve some chasing and posturing. The dominant male will frequently display to the females to maintain his status and keep the harem in line. While usually harmless, this internal squabbling requires adequate space and hiding spots for subordinate individuals. They should not be housed with overly aggressive predators that might bully or consume them.
- Diet
- Carnivore
- In the wild, Pseudanthias pleurotaenia is a dedicated zooplanktivore that constantly picks tiny organisms from the water column. In the home aquarium, they require a varied diet consisting of high-quality frozen or live meaty foods. Suitable options include mysis shrimp, enriched brine shrimp, copepods, and finely chopped seafood. Getting them to accept dry prepared foods like high-quality flakes or small pellets can take time and patience. A diverse nutritional profile is crucial for maintaining their vibrant coloration and immune health.
- Life expectancy
- 5-7 years
- The Squarespot Anthias can live for 5 to 7 years in captivity when provided with high-quality care and a stable environment. Achieving this longevity requires a large tank (at least 100 gallons / 400 liters), pristine water chemistry, and a consistent feeding schedule of nutritious foods. Minimizing stress from aggressive tankmates is also key to preventing stress-induced illnesses. Regular monitoring and care will help this beautiful fish thrive for its full potential lifespan.
- Adult size
- 20 cm
- The catalog's scalar value is 20 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 20 cm for this species, recorded as total length (TL). The taxonomic record consulted is Pseudanthias pleurotaenia (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Harem
- This species exhibits a fascinating social structure characterized by protogynous hermaphroditism, where all individuals are born female. A typical group consists of a single dominant male maintaining a harem of several females. If the dominant male is removed or dies, the largest and most dominant female will morph into a male to take his place. For the home aquarium, it is best to purchase a group of females and allow this natural transition to occur. Keeping multiple males usually results in fatal aggression unless the tank is massive.
- Feeding frequency
- 3-4 times daily
- Due to their incredibly active metabolism and natural grazing behavior, Pseudanthias pleurotaenia requires multiple feedings throughout the day. It is highly recommended to feed them small amounts at least three to four times daily. Infrequent, large feedings are poorly digested and can lead to malnutrition or starvation over time. Automated feeders can be very useful for dispensing small amounts of dry food while the aquarist is away. Consistent, frequent meals are the key to long-term success with this species.
- Bioload
- High
- Pseudanthias pleurotaenia contributes a moderate amount to the overall bioload of a marine aquarium system. Due to their highly active nature and constant swimming, they require frequent feedings which indirectly increases the organic waste produced. Excellent filtration and regular water changes are strongly recommended to process these nutrients. Maintaining a robust protein skimmer will help manage the dissolved organics effectively. Proper husbandry ensures that the bioload remains manageable over the long term.
- Flow
- Strong
- This species originates from dynamic reef environments where strong water movement is a constant factor. Pseudanthias pleurotaenia thrives in aquariums that provide moderate to strong, turbulent water flow across the aquascape. Brisk currents simulate their natural habitat and encourage their natural schooling and feeding behaviors in the water column. Powerheads or wavemakers should be positioned to create broad, sweeping flow patterns rather than harsh, direct streams. Adequate flow also keeps particulate food suspended longer, giving them more time to feed.
- Jump risk
- Yes
- Like many highly active reef fishes, Pseudanthias pleurotaenia presents a moderate to high risk of jumping out of an open aquarium. They are easily startled by sudden movements, lighting changes, or aggressive tank mates, which can trigger a flight response. It is strongly advised to keep a tight-fitting lid or a custom mesh screen over the tank at all times. Even small gaps around equipment and overflow boxes should be covered to prevent tragic accidents. Taking these precautions is a simple but vital part of their husbandry.
- Reproduction
- Oviparous
- Breeding Pseudanthias pleurotaenia in a home aquarium is exceptionally rare and presents significant challenges for even advanced hobbyists. They are pelagic spawners that release their eggs and sperm into the water column during synchronized mating rituals. The resulting larvae are microscopic and require highly specialized, perfectly sized live planktonic foods to survive. Furthermore, the larval stage is extremely long and sensitive to minute changes in water quality. Consequently, nearly all specimens available in the trade are wild-caught rather than captive-bred.
- Compatibility & tankmates
- Reef safe
- This species is generally considered completely reef safe and makes a stunning addition to mixed reef aquariums. Pseudanthias pleurotaenia will typically ignore corals, sessile invertebrates, and most motile invertebrates like ornamental shrimp. They are generally peaceful towards heterospecifics but can display significant aggression towards other Anthias species. It is usually best to keep them as the only Anthias species in the tank unless the aquarium is exceptionally large. Careful observation is needed when introducing new tank mates to ensure harmony.
- Tank level
- All levels
- Throughout the day, Pseudanthias pleurotaenia will predominantly occupy the middle to upper levels of the water column. They are highly visible fish that love to hover above the reef structure, facing into the current to catch passing food. At night or when frightened, they will quickly dart into the rockwork to seek shelter in crevices and caves. Providing plenty of open swimming space alongside complex rock formations is essential for their comfort. Their active presence brings a wonderful sense of movement and life to the upper reef zones.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.4 ± 0.45 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.5
- Bayesian Length-Weight
- a = 0.01413, b = 3
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
