Squareback Anthias 

Also known as Squarespot Anthias, Square-block Anthias

The Squareback Anthias is a distinctive and hardy species featuring a unique squared-off body shape and beautiful pink-to-orange coloration with a characteristic square spot. This relatively peaceful anthias is more adaptable than many species, making it suitable for moderately experienced aquarists.

Key Features

• Scientific Name: Pseudanthias pleurotaenia
• Common Names: Squareback Anthias, Squarespot Anthias, Lori’s Anthias
• Adult Size: Up to 8 inches
• Lifespan: 5-7 years with proper care
• Temperament: Peaceful to semi-aggressive; more territorial than most anthias
• Reef Compatibility: Completely reef safe; will not harm corals or invertebrates
• Minimum Tank Size: 100 gallons 
• Experience Level: Moderate; hardier than many anthias species

Habitat & Tank Requirements

• Tank Environment: Provide ample open swimming space with moderate to strong water flow. Include substantial rockwork with caves, ledges, and overhangs. This larger anthias species requires more swimming room than smaller relatives.
• Water Parameters:
  • Temperature: 72-78°F (22-26°C)
  • Salinity: 1.023-1.025
  • pH: 8.1-8.4
  • Maintain stable, high-quality water conditions
• Equipment Recommendations:
  • Quality protein skimmer
  • Efficient filtration system
  • Powerheads for adequate water circulation These help maintain the pristine conditions this species prefers.

Diet & Feeding

Squareback Anthias are planktivores with hearty appetites. Recommended foods include:

• Staples: High-quality marine pellets, vitamin-enriched flake foods
• Frozen Foods: Mysis shrimp, brine shrimp, krill, cyclops, finely chopped seafood
• Live Foods: Enriched brine shrimp, copepods (helpful during acclimation)
• Feeding Frequency: 2-3 times daily
• Special Note: Generally adapts well to prepared foods and is less finicky than smaller anthias species

Social Structure & Group Dynamics

• Best Kept in Groups: Ideal ratio is 1 male to 3-5 females
• Sexual Dimorphism: Males display more intense pink-orange coloration with a prominent square or rectangular dark spot on the side (giving the species its common name). Females are paler with less defined markings.
• Sequential Hermaphroditism: All are born female; dominant female transforms to male when needed
• Territorial Behavior: Males can be more aggressive than typical anthias, especially in smaller tanks
• Tank Size Important: Larger aquariums help reduce territorial disputes

Notes & Considerations

• Larger and more robust than most anthias species, making it somewhat hardier.
• The distinctive square spot on the body is a key identifying feature.
• More territorial than many other anthias; provide adequate space to minimize aggression.
• Active swimmers that add constant movement to larger aquariums.
• A secure aquarium lid is essential; capable jumpers.
• Can be kept with other anthias species in very large systems with careful monitoring.
• Males may show aggression toward other similarly colored fish in smaller tanks.
• Generally peaceful toward non-anthias tankmates.

Why Choose a Quarantined Squareback Anthias?

Purchasing a quarantined specimen from us means you’re starting with a healthier, better-acclimated fish. All fish are observed, treated as needed, and conditioned to accept prepared foods before sale, giving you a stronger chance of long-term success with this distinctive and colorful species.