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About Squareback Anthias

The Squareback Anthias is a striking reef fish recognised for its deep pink to purple colouration and distinctive square-shaped dark marking on the side of the body. Males are particularly spectacular, often developing intense pink, purple and red colouration with elongated fins.

Like other anthias, Squarebacks are active planktivores that spend much of their time swimming in the water column and feeding on passing plankton. They look their best when maintained in a group with plenty of open swimming space.

Squareback Anthias are protogynous hermaphrodites, meaning they begin life as females. If the dominant male is removed, the largest female can transition into a male and take over the group.

They benefit from frequent feeding, excellent water quality and strong oxygenation. A varied diet of mysis shrimp, enriched brine shrimp, finely chopped seafood and quality marine pellets will help maintain their colour and condition.

Quick Care Guide

Scientific Name: Pseudanthias pleurotaenia
Common Name: Squareback Anthias
Family: Serranidae
Type: Marine Reef Fish / Anthias
Adult Size: Approximately 15 cm
Temperament: Peaceful to Semi-Territorial
Care Level: Intermediate
Minimum Aquarium: 300 L+
Temperature: 24–28°C
pH: 8.0–8.4
Salinity: 1.023–1.026 SG
Diet: Planktivore / Carnivore
Tank Level: Midwater to Upper Levels
Reef Safe: Yes
Suitable For: Large reef aquariums and peaceful marine community systems

Frequently Asked Questions

How many Squareback Anthias should I keep?

They are social fish and are best kept in a group or harem, typically with one male and several females. A sufficiently large aquarium is important when keeping a group.

Can Squareback Anthias change sex?

Yes. They are protogynous hermaphrodites. Females can transition into males when the dominant male is absent.

Are Squareback Anthias reef safe?

Yes. They are generally reef safe and are excellent additions to coral aquariums.

What do Squareback Anthias eat?

They benefit from frequent feeding of mysis shrimp, enriched brine shrimp, finely chopped seafood and quality marine pellets. Multiple smaller meals throughout the day are ideal.

Do Squareback Anthias need a large aquarium?

Yes. They are active swimmers and can reach around 15 cm, so substantial swimming space is required, particularly when keeping a group.

Common Mistakes

Feeding only once per day
Anthias have a high metabolism and benefit from several smaller meals throughout the day.

Keeping multiple males together
Males can become territorial. A single male with females is generally the preferred social structure.

Not providing enough swimming space
Squareback Anthias are active open-water swimmers and require plenty of unobstructed water.

Adding them to an immature aquarium
Stable water quality, excellent oxygenation and reliable feeding are important for long-term success.

Keeping them with aggressive tank mates
Their peaceful nature makes them vulnerable to harassment from highly aggressive marine fish.