Temp
Food
Flow
Difficulty
Getting to Know the Square Anthias
The Square Anthias (Pseudanthias pleurotaenia), also known as the Square-spot Anthias, is a vibrant and active fish that brings life and colour to any marine aquarium. Recognised by its distinctive square-shaped spot on the side and striking orange and pink hues, this anthias is a favourite among reef enthusiasts. Native to the Indo-Pacific region, it thrives in the middle to upper levels of coral reefs where it feeds and flutters in small groups.
Choosing Your Square Anthias
When selecting a Square Anthias, look for healthy individuals with bright, saturated colours and no signs of stress or damage. A lively fish that swims actively and responds well to feeding is ideal. Because these fish do best in groups, consider purchasing at least three or more to create a natural social environment, which helps reduce stress and encourages natural behaviour.
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Tank Setup and Environment
Square Anthias require a well-established tank of at least 200 litres with plenty of live rock to provide hiding places and grazing surfaces. They appreciate open swimming space combined with areas of shelter where they can retreat when needed. Good water quality is essential, as these fish can be sensitive to sudden changes in water parameters. Moderate to strong lighting helps promote coral growth, which benefits the overall tank ecosystem they inhabit.
Feeding and Nutrition
Nori seaweed sheets clipped to the glass daily
Spirulina-based flakes and pellets
Frozen mysis shrimp
Frozen brine shrimp
Chopped clam or prawn (offered occasionally)
Marine algae blends designed for tangs
Square Anthias are carnivores and thrive on a diet rich in meaty foods. Offering a variety of frozen and prepared foods multiple times per day helps replicate their natural feeding habits and keeps them healthy and vibrant. Feeding near mid-water or slightly higher encourages natural swimming patterns.
Behaviour and Compatibility
Square Anthias are peaceful, social fish that do best in groups of their own species or with other peaceful reef dwellers. They can be shy initially but become more confident when kept in a group. Compatible tank mates include:
Clownfish
Gobies
Blennies
Small wrasses
Peaceful damselfish
Avoid keeping them with aggressive or much larger fish that may outcompete them for food or intimidate them.
Water Conditions and Flow
Temperature 24–27°C
pH 8.1–8.4
Salinity 1.023–1.025
Moderate to strong flow is ideal to maintain oxygenation and circulate food efficiently
Stable water conditions and consistent flow are important for the health of the Square Anthias. The flow mimics their natural reef environment and helps distribute food particles throughout the tank.
Health and Longevity
With proper care, Square Anthias can live for 4 to 6 years in captivity. They are generally hardy but can be prone to common marine diseases like ich if stressed. Quarantine new arrivals and maintain excellent water quality to reduce risks. A varied diet and a calm environment contribute to their wellbeing.
Final Thoughts
The Square Anthias is a lively and eye-catching addition to medium and large reef aquariums. Their beautiful colours, active swimming, and peaceful nature make them popular among marine hobbyists. By providing a spacious tank, stable water conditions, and a varied diet, you’ll enjoy watching this energetic fish flourish in your reef setup.
