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*This fish is a marine species*

The Squareback Anthias, also known as Squarespot or Squareblock Anthias are suited for the intermediate aquarist. It is a semi-aggressive species with a beautiful colour variation depending on sex. Males are predominately pink with a light-coloured rectangle on its side and a lavender belly.

The Squareback Anthias is native to many areas within the Pacific Ocean from Indonesia, Samoa and New Caledonia.


Features of Square Block Male:

  • Pink in colour
  • Grow up to 20cm
  • Care level: Moderate
  • Reef compatible


Tank Mate Compatibility:

Here’s a list of some of the best tank mates for your Square block Anthias:

  • Large and dwarf Angels
  • Tangs
  • Butterflies
  • Clownfish
  • Damsels

Square block Anthias are a semi-aggressive fish. They can be kept as a school of females or within a mated pair but is important only have one male kept within the tank due to aggression. Generally, the largest female will replace the dominant male and is capable of doing so in 2-3 weeks.



Square block Anthias are carnivores so their diet should consist of frozen mysis and brine shrimp and copepods. Small amounts of high-quality flake foods can also be added up to 3-5 times a day. They also feed on zooplankton within the tank. These fish are grazers and do best being fed multiple times throughout the day.




Square block Anthias are best suited to a longer aquarium as they appreciate plenty of room to swim. A minimum tank size of 370L is required when housed singly or larger for additional fish. These fish happily live in groups of up to 10 females and one male but the tank size must be increased up to 680L.

After an Aquarium for your fish? Browse our Aquarium Tank Selection here.


Square Block Anthias prefer water temperatures between 22°C - 27°C.

Looking for a Heater for your fish? Check all available Tank Heater here.


Replicate natural conditions with artificial lighting (8-10 hours of light every 24 hours.)

Need An Aquarium Light for your tank? Browse our Fish Tank Aquarium Lighting

Filtration & Water Movement:

Square block Anthias require good filtration and water quality. They are active fish, particularly when it comes to feeding and defending territory. They swim counter-current so it is recommended to have a good powerhead.

Explore aquarium filtration products here.


Incorporate rubble and some live rock substrate. Replicate reef habitats and boost biological filtration with coral sand.

View our range of aquarium substrates here.


Decorations for Square Block Anthias:

Square block Anthias require slow acclimation and therefore need plenty of places to hide, particularly within their first week. They are reef dwellers and will hide around live rock or coral.

View our large range of aquarium decorations here.

Additional Information

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