Brackish River Sole

Geographical Origin and Habitat: Silt-bottomed rivers and coastal estuaries of Borneo, Sumatra, and Thailand. Lives on sandy riverbeds.

Taxonomy and Morphology: Family Cynoglossidae. Asymmetrical flatfish with both eyes located on the left side of the head. Grows to 25 cm.

Social Behavior: Peaceful and extremely inactive during the day. Buries itself in the sand with only its eyes exposed.

Coloration and Sexual Dimorphism: Mottled brown-grey ocular side for mud camouflage. Blind side is pale white. No external dimorphism.

Aquarium Setup: Demands a thick layer (at least 5 cm) of soft sand. Avoid sharp gravel. Keep the layout open with minimal stones.

Diet and Feeding: Specialized benthic carnivore. Feeds on live or frozen bloodworms, tubifex, and brine shrimp. Hard to train onto dry foods.

Water Quality: Prefers light brackish water (SG 1.002-1.005) but adapts to hard freshwater. Keep nitrates low and oxygen levels stable.

Compatibility and Cohabitation: Safe with peaceful midwater species like glassfish. Do not house with aggressive bottom-dwelling fish.

Aquarium Breeding: Not bred in captivity due to lack of knowledge on spawning triggers.

Risks and Diseases: Highly prone to skin infections and red leg/underside sores if the substrate is dirty. Weekly sand vacuuming is required.