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Amethyst Anthias
Pseudanthias pascalus
The amethyst anthias (Pseudanthias pascalus) is a large, vibrant purple marine fish that inhabits outer reef slopes and requires frequent feedings and high water flow.
Water Temperature
22 - 27 °C
pH Value
8.1 - 8.4
Water type
Marine
Tank level
Bottom and middle
Adult size
20 cm
Minimum tank volume
>= 500 L
Minimum group
>= 4
KH
8 - 12 dKH
Species description
Geographical Origin and Habitat: This species is widely distributed throughout the tropical Western and Central Pacific Ocean, ranging from the Ryukyu and Ogasawara Islands of Japan down to the Great Barrier Reef in Australia, New Caledonia, and eastward to the Tuamotu and Society Islands in French Polynesia. It primarily inhabits deep outer reef slopes, drop-offs, and vertical walls at depths between 5 and 60 meters, where strong currents deliver zooplankton.
Taxonomy and Morphology: Pseudanthias pascalus belongs to the Serranidae family, subfamily Anthiadinae. It features an elongated, moderately deep body profile compared to other members of the genus. The caudal fin is deeply lunate, with mature males developing long filamentous extensions on the upper and lower lobes. The mouth is large and adapted for planktivorous feeding. Adults can reach a length of 20 cm.
Social Behavior: It is a highly gregarious, active schooling fish that forms massive aggregations in the water column above coral formations. Like other anthias, it is a protogynous hermaphrodite, with all individuals beginning life as females and the most dominant female transitioning into a male. They live in strict harems, with a single dominant male guarding a group of females.
Coloration and Sexual Dimorphism: The body coloration is a brilliant, uniform amethyst-purple. Sexual dimorphism is highly pronounced: terminal males display a reddish snout, yellow spots on the head, small red or yellow spots scattered along the body, and bright red tips on the caudal fin lobes. Females are a uniform, slightly lighter lavender-purple and lack the red tail tips.
Care, breeding and tankmates
Aquarium Setup: Requires a very large aquarium of at least 500 liters (130 gallons) due to its active nature and large size. The aquascape should feature a substantial live rock structure along the back of the tank to provide multiple caves and overhangs for shelter, while leaving a wide open area in the front and center for swimming. A tight-fitting lid is mandatory, as they are prone to jumping.
Diet and Feeding: Carnivorous. As a specialized planktivore, it has a high metabolic rate and must be fed multiple times per day (3-4 times minimum). Offer a variety of frozen foods such as mysis shrimp, brine shrimp, copepods, and finely chopped seafood. High-quality dry foods are rarely accepted initially, and a long acclimation period is needed. Starvation is a major risk.
Water Quality: Demands pristine, highly oxygenated water conditions. Maintain standard marine parameters: water temperature between 22°C and 27°C, pH between 8.1 and 8.4, specific gravity of 1.020 to 1.025, and KH between 8 and 12. A high-capacity protein skimmer and regular water changes are required to keep nitrates low, combined with strong water flow to simulate reef currents.
Compatibility and Cohabitation: 100% reef-safe and compatible with all corals and sessile invertebrates. It must be kept in groups consisting of one male and at least 3 to 5 females. Do not house more than one male in the same tank, as they will fight. Suitable tankmates include peaceful tangs, clownfish, gobies, and other non-aggressive reef fish. Avoid boisterous tankmates.
Aquarium Breeding: Spawns in the open water column. At dusk, the male and a receptive female perform a rapid vertical ascent to release their gametos. The eggs are pelagic and hatch within 24 hours. Breeding in home aquariums is extremely difficult due to the challenges of rearing the microscopic planktonic larvae, which require specialized live feeds.
Risks and Diseases: Starvation is the leading cause of mortality if they are not fed frequently enough. They are highly sensitive to shipping stress and poor acclimation, making them prone to marine ich (Cryptocaryon irritans) and marine velvet (Oodinium). Quarantine new arrivals and ensure they are eating frozen food before introduction.
Geographic Origin and Distribution
This species is widely distributed throughout the tropical Western and Central Pacific Ocean, ranging from the Ryukyu and Ogasawara Islands of Japan down to the Great Barrier Reef in Australia, New Caledonia, and eastward to the Tuamotu and Society Islands in French Polynesia. It primarily inhabits deep outer reef slopes, drop-offs, and vertical walls at depths between 5 and 60 meters, where strong currents deliver zooplankton.
Origin
Tropical oceans and reefsEast AsiaAustralia, New Guinea, and Oceania
Fish profile
- Temperament
- Aggressive
- The temperament of Pseudanthias pascalus 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 pascalus 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
- 3-5 years
- The Amethyst Anthias has a lifespan of approximately 3 to 5 years in captivity, though they are notoriously difficult to maintain long-term. To maximize their lifespan, they require absolute stability in water parameters, exceptionally clean water, and a stress-free environment. They are very sensitive to shipping and acclimation stress, which often reduces their lifespan in captivity. Experienced husbandry and a dedicated environment are key to helping them reach their full 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 link follows a synonym to the FishBase SPECIES table (v25.04 snapshot) record for Mirolabrichthys pascalus (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 pascalus 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
- Pseudanthias pascalus 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 pascalus 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 pascalus 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 pascalus 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 pascalus 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
- Middle/Bottom
- Throughout the day, Pseudanthias pascalus 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
- 3.3 ± 0 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.625
- 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.
