Squareback Anthias Male (Pseudanthias Pleurotaenia)

Also Known As: Purple Square Anthias, Squarespot Anthias

Compatibility and Behavior
The male Squareback Anthias (Pseudanthias pleurotaenia) is genuinely one of the most striking anthias in the trade. The body shows a rich blend of deep pink and orange running into a softer lavender belly, broken up by the unmistakable pale pink "square" patch along the flanks that gives the species its name. The fins glow in shades of purple, blue, and yellow, and a reddish stripe runs from the snout through the eye, finishing off an elegant, elongated profile that really pops against open water in the mid to upper levels of the tank. Males are more intensely colored than females and serve as the focal point of the harem, constantly flashing and displaying to keep the group in order.

Like other anthias, Squarebacks are hermaphroditic and highly social, naturally forming harems of one dominant male and several females. They tend to do best replicated that way in captivity, rather than as a single male thrown into a crowded community of pushy tankmates. They're considered reef safe with corals and clams, since they spend their time picking zooplankton out of the water column rather than bothering sessile inverts. Males can lean semi-aggressive toward other anthias or fish with a similar shape and color, especially competing males, so the usual approach is one male per group and avoiding closely related anthias species in smaller systems.

Aquarium Requirements
These fish do best in large, mature reefs with excellent oxygenation, strong but laminar flow, and plenty of open swimming space. Plan on at least 100 gallons for a single specimen, with 150 to 180+ gallons more appropriate for a harem. Low to moderate, indirect lighting tends to preserve their color over time. Very bright, direct lighting can gradually wash them out. Arrange rockwork to create ledges and overhangs adjacent to open water, so the group has a quick retreat available while still spending most of the day schooling and feeding in the midwater column.
Like most Anthias, Squarebacks are high-metabolism planktivores, so multiple small daily feedings of finely chopped seafood, mysis, brine, and quality marine pellets are essentially non-negotiable. Squarebacks are high-metabolism planktivores, so multiple small daily feedings of finely chopped seafood, mysis, brine, and quality marine pellets are essentially non-negotiable. One thing worth knowing: in many cases, Anthias only eat food out of the water column, and once it has fallen to the tank floor they are no longer interested. That makes flow patterns and feeding technique just as important as the food itself.Stable, high-quality filtration goes hand in hand with that feeding schedule, since the bioload from frequent meals adds up quickly.

Specifications
Approximate Size: 3.5-5"
Diet: Carnivore/zooplanktivore (finely chopped seafood, mysis, brine, high-quality marine pellets. Multiple feedings per day)
Origin: Western and Central Pacific
Care Level: Moderate (best for intermediate to advanced reef keepers)
Reef Safe: Yes (generally safe with corals and clams)
Temperament: Semi-aggressive; dominant males can be territorial toward other anthias or similar-shaped fish
Minimum Tank Size: 100 gallons for a single; 150–180+ gallons recommended for a harem
Special Considerations: Best kept as one male with a small group of females; avoid housing multiple males together; requires multiple small feedings per day; lower indirect lighting helps preserve coloration