TankBud

Square anthias

Pseudanthias pleurotaenia

Also known as Pink Square Anthias, Squareback Anthias, Squarespot Anthias, Purple Blotch Basslet

SaltwaterFish

Square anthias (Pseudanthias pleurotaenia)
Jenny (JennyHuang) from Taipei · CC BY 2.0

Care at a glance

Temperature
72–79°F
22–26°C
pH
8.1–8.4
Adult size
7.9 in
20 cm
Minimum tank
100 gal
380 L
Temperament
Mostly peaceful
Social behavior
Social
Swim level
Middle
Diet
Carnivore
Difficulty
Medium
Breeding
Hard
Rarity
Common
Reef safe
Reef safe
Family
Serranidae
Origin
Western Pacific and eastern Indian Ocean reefs, from Indonesia to Samoa, north to the Ryukyu Islands, south to New Caledonia

Overview

The square anthias is one of the largest anthias kept in the hobby, and it suits a big reef tank. It is a step up from the easiest fish.

Did you know

The dominant square anthias male shows a square block of purple-pink color as a signal of status. Subordinate males and females never show it, so a fully colored square patch reliably marks the fish running the harem.

Caring for the square anthias

Give the square anthias at least 100 gal (380 L), with a long, open swimming lane above a substantial rock structure. Males patrol and defend a real territory, so they need the room. Keep the lighting on the lower, indirect side, since harsh light washes out its color and adds stress.

Hold the water at 72 to 79°F (22 to 26°C) and a pH of 8.1 to 8.4. New fish are timid and easily stressed, and slower to start feeding than other anthias. Feed small meaty foods several times a day, since it does poorly on one or two large meals.

Males fight other males of the species to the death, so keep only one per tank, ideally with four to six females. Females are yellow-orange with a lavender belly, while males turn deep pink to reddish-purple. Females also peck at smaller fish of their own kind, so add similarly sized fish together.

The square anthias is mostly peaceful and fully reef safe with corals and invertebrates. It settles best in a tank where other anthias or peaceful fish are already established. Keep it away from aggressive tank mates, large angelfish and predatory fish that could bully or eat it. Breeding it is hard.

Good to know

The square anthias, Pseudanthias pleurotaenia, is a member of the family Serranidae. It is a protogynous hermaphrodite that forms harems, and the females hold their own pecking order within a group. The largest female steps up to replace a lost male. The species takes its common name from the square patch of color on the male's flank. It is also sold as the squareback anthias, squarespot anthias and purple blotch basslet.

In the wild

The square anthias ranges across the western Pacific and into the eastern Indian Ocean. It is found from Indonesia to Samoa, north to the Ryukyu Islands and south to New Caledonia. It lives on outer reef slopes and drop-offs, from the shallows to past 100 m, but is most common in the top 25 m.

Weekly picks

Tank mates

The square anthias is a mostly peaceful, social species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.

Check the full mix in the stocking calculator

Common questions

What size tank does a square anthias need?

A square anthias needs at least 100 gal (380 L). It spends most of its time in the middle.

What temperature and pH does a square anthias need?

A square anthias is comfortable at 72–79°F (22–26°C) with a pH of 8.1–8.4.

What does a square anthias eat?

A square anthias eats small meaty foods several times a day. It does poorly on one or two large meals.

How big does a square anthias get?

An adult square anthias reaches about 7.9 in (20 cm).

How can you tell a male square anthias from a female?

Females are yellow-orange with a lavender belly, while males turn deep pink to reddish-purple.

Related species