Green Scat

Geographical Origin and Habitat: Indo-Pacific (Kuwait, Japan, Fiji). Estuary par excellence. Lives in dense mangrove forests, polluted ports, muddy river mouths and currently swims up into freshwater sections.

Taxonomy and Morphology: Spotted Scat (Scatophagus argus). Scatophagid. Compressed and tall disc body (almost square), with a very small head compared to its size. The first rays of the thick dorsal fin are robust (and slightly venomous) spines.

Social Behavior: Demolition squad. Very sociable and schooling fish, swims constantly up and down the glass waiting for food. Extremely active, curious and fearless; explores every element of the tank with its mouth.

Coloration and Sexual Dimorphism: The "Leopard" (Argus). Silvery, bronze or bright olive green background, densely covered (especially in youth) with large black circular spots (polka dots). As an adult (at 30 cm / 12 inches) the spots fade and merge, making it a dark bronze color. There is a variant with a reddish head (Red Scat).

Aquarium Setup: Huge Brackish Tank (Minimum 150 cm / 60 inches). Freshwater tolerated only by juveniles. Plants forbidden (they eat all of them except Java fern and fake ones). Layout with large intertwined trunks (mangroves) and solid rocks. A lot of empty space for swimming is needed.

Diet and Feeding: The Everything-Grinder Omnivore. Its Latin name literally means "Feces eater" (because it sweeps port drains). Devours algae, salad, peas, floating pellets, minced fish, shrimp. Greatly appreciates filamentous algae.

Water Quality: Saline Transition. Juveniles in stores are kept in freshwater (high GH, alkaline). As they grow (beyond 10 cm / 4 inches), they MUST be brought to heavy brackish water (Specific Gravity 1.010 - 1.015) up to pure marine water, otherwise they will waste away irremediably.

Compatibility and Cohabitation: Brackish Community. The perfect companion for estuary fish: Monodactylus (Argenteus and Sebae), Toxotes (Archerfish), and Brackish Pufferfish (Tetraodon biocellatus). Devours any small fish or crustacean.

Aquarium Breeding: Never documented in private closed systems. They require migration from the estuary (where they grow) to the open sea (where they lay pelagic eggs), and vice versa for the larvae. Space and chemical variations impossible to replicate.

Risks and Diseases: Freshwater Syndrome. Many buy them as "freshwater fish". After a year in water without marine salt, their immune defenses collapse: the fish becomes, develops white clouds on its eyes (Eye Cloud), stops eating and dies from hepatic-osmotic block.