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Family: Serrasalmidae

Common Name: Silver Dollar

Origin and Habitat: Found over a wide area within parts of Brazil, Bolivia, Guyana, Peru and Venezuela: rivers of the north Guyana Shield, Rio Paraguay basin, and the western basin of the Amazon. It inhabits densely planted tributaries with slow water movement.

Compatibility/Temperament: This is a peaceful schooling fish growing to almost 6 inches in size. They have a tendency to consume several plants, mostly those with soft foliage as they are largely vegetarians by nature. They are shoaling fish and must be in a group, minimum six,and they should not be kept with fish that are smaller, as these will probably be eaten.

Silver Dollar Diet

These fish are primarily vegetarians, though in the wild they will eat insects and worms. Their diet should include mainly vegetable-based foods, such as flakes designed for herbivores, romaine lettuce and other vegetable matter.


Grows to around six inches.

Minimum Tank Suggestion

Length 4 feet.

Water parameters for Silver Dollar

Soft (hardness to 15 dGH) acidic (pH below 7.0) water, temperature 24-28C/74-82F.


There are several distinct species within the genus Metynnis that are commonly called "Silver Dollar" fish. They all share a similar shape and silver colour, and similar behaviours, habits and requirements; the long adipose fin distinguishes these species from all other Serrasalmidae. Along with the subject species (shown in the first photo below), the other most frequently encountered is M. argenteus (second photo). It reaches a length of 5 inches, and lacks the dark shoulder patch of M. hypsauchen. There is also a striped species and a spotted species.

The Metynnis species are closely related biologically to the pacu and piranha, sharing the peaceful traits of the former rather than the aggressiveness of the latter.

Silver dollars are nervous fish, so subdued lighting and plenty of hiding places made from plants (real and fake) and wood will allow this fish to feel secure. Tough plants like Java Fern and Anubias, though foreign to their native waters, will likely elude their vegetarian eating habits.

Since they occur in shallow waters in the wild, the depth of the aquarium is of less significance that the length and width. A group of five will require a 4 foot tank at minimum, but preferably 5-6 feet as they grow or with a larger shoal. They occupy the upper and middle regions in the tank; the larger catfish and plecostomus make suitable tankmates.

Breeding: In the wild they breed in shallow, sun-drenched flood sections of rivers. In a home aquarium, they have been known to breed in aged water. When they breed they tend to use broad-leaved plants to lay their eggs on and the eggs should hatch in about 4 days. The fry will be free swimming in another 10 days. The optimal breeding temp is between 81 and 90 degrees. Males have an elongated and more colourful anal fin.

Contributing Members

The following members have contributed to this profile: Byron


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