Silver Dollar

The Silver Dollar is a round, disc-shaped characin native to the Amazon basin, named for its flattened, coin-like body silhouette and bright silvery coloration. The body is strongly laterally compressed and nearly circular in outline, covered in reflective silver scales that can flash faint hints of blue or green iridescence under bright light. Fins are typically translucent to lightly tinted, with a small, low dorsal fin and a broad anal fin that extends along much of the ventral profile. Closely related to piranhas within the same family, Silver Dollars share a similar deep body shape but are almost entirely herbivorous, lacking the predatory dentition of their more infamous relatives.

• Strongly compressed, nearly circular disc-shaped body
• Bright, reflective silvery scales, sometimes with faint blue-green iridescence
• Small, low-profile dorsal fin
• Broad anal fin running along much of the ventral body edge
• Deeply forked caudal fin
• Rounded snout with small, herbivore-adapted teeth

Silver Dollars closely resemble young piranhas in overall body shape but lack the piranha's sharply pointed, interlocking teeth and typically show a more uniformly silver, unmarked body rather than the spotting or dark coloration common in many piranha species.

Silver Dollars are native to slow-moving rivers, flooded forest habitats, and tributary streams within the Amazon basin, particularly associated with the Tapajos and Tocantins river systems in Brazil. They favor warm, softly acidic to neutral water and are strongly associated with seasonally flooded forest, where they forage extensively among submerged and overhanging vegetation during high-water periods. Shoaling in open and semi-open water near plant cover is typical, with the species often found among leaf litter and root tangles along river margins. Their reliance on flooded forest vegetation for feeding links their seasonal movements closely to the annual flood pulse cycle characteristic of Amazonian river systems.

Silver Dollars are social, schooling fish that move in cohesive groups through open water, using their numbers as a defense against predators given their otherwise vulnerable, unarmored disc-shaped bodies. They are primarily herbivorous, grazing heavily on soft aquatic and overhanging terrestrial vegetation, algae, and fallen fruit, playing a role in seed dispersal within their flooded forest habitat. Feeding activity intensifies during seasonal flooding, when access to submerged plant material increases substantially. Reproduction follows the typical scatter-spawning characin pattern, with adhesive eggs released among vegetation and no parental care provided afterward. Their strong grazing pressure on aquatic plants makes them notable herbivores within the broader Amazonian flooded forest food web.