Silver Dollar

Geographic Origin and Biotope: Tapajós River basin and other clear Amazonian basins (Brazil). Swims preferably in slow-flowing rivers, coastal areas and estuaries rich in protruding branches and floating plant debris.

Taxonomy and Morphology: Silver Dollar (Metynnis argenteus). Related to Piranhas, but pacifist. Shares the body shape: compressed like a perfect disk (coin-like), but boasts flat molar-like teeth for crushing rather than sharp fangs.

Social Behavior: Extremely fearful and highly gregarious (Dither fish). It is one of the most darting and easily terrified fish there is. Must be kept in minimum groups of 6-8 to prevent them from hiding in the dark.

Coloration and Sexual Dimorphism: A dazzling silver plate (Silver Dollar). The only break in color is a faint reddish or golden tinge at the throat. Males develop a reddened/elongated anal fin edge.

Aquarium Setup: Titanic tanks (min. 150 cm / 60 inches). Being excellent panicked sprinters, they will struggle to dodge solid furnishings in small tanks. Do not use sharp woods or volcanic stones (they will cut their flanks darting). Plants FORBIDDEN (they will eat them all).

Diet and Feeding: The leaf destroyer. Absolute vegetarian (folivore). Will mow down Echinodorus, Vallisneria and even Anubias. Administer large amounts of blanched lettuce, zucchini, peas and spirulina. Rare fleshy supplements to avoid adiposity.

Water Quality: Sensitive to oxygen-poor water. Being large schooling fish, the organic load is heavy. Powerful filters and frequent water changes. The water should ideally be amber to shield the light and calm them.

Compatibility and Tankmates: Excellent mid-water roommate for aggressive South American Cichlids (Oscars, Green Terrors, Severums). The Silver Dollar will act as a "Dither Fish": its presence will calm the giant Cichlids. Too large for small Tetras.

Aquarium Reproduction: Rare but possible in giant tanks. Breeders drop hundreds of eggs among the skeins of suspended roots or fake floating plants (which they cannot eat). Non-adhesive eggs that fall to the bottom.

Risks and Diseases: Fatal accidents against the glass (Wall-smashing). The sudden turning on of the lights in the room will lead them to dart blindly; they will hit glasses or rocks suffering lethal head trauma or evisceration. Create progressive "Sunrise/Sunset" lights.