Silver Dollar
Metynnis argenteus
The Silver Dollar (Metynnis argenteus) is the emblem of the schooling fish for large aquariums. As the name suggests, it possesses a round, high, laterally compressed body that, covered with tiny scales, shines like a disc of pure metallic silver in the light. This close herbivorous relative of Piranhas sports an elegant and nervous swimming style, moving in unison in tight schools. Its adult size (15 cm / 6 inches) and propensity to eagerly devour any aquatic plant make it the perfect companion for bare tanks dedicated to large South American cichlids.
Temperatura da água
24 - 28 °C
Valor de pH
6 - 7.5
Tipo de água
Água doce
Nível do tanque
Superfície e meio
Tamanho adulto
15 cm
Volume mínimo do tanque
>= 300 L
Grupo mínimo
>= 6
GH
4 - 15 dGH
KH
2 - 7 dKH
TDS
80 - 295 ppm
Condutividade
125 - 461 uS/cm
Descrição da espécie
Geographical Origin and Habitat: 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.
Cuidado, criação e companheiros de tanque
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 Cohabitation: 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 Breeding: 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.
Origem e distribuição geográfica
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.
Origem
Amazônia, Orinoco e GuianasEuropa, Mediterrâneo e Ásia Ocidental
Perfil de peixe
- Temperamento
- Peaceful
- They are peaceful and somewhat timid fish despite their large, imposing appearance. They rely heavily on the security of their school and can become extremely stressed or easily frightened if kept alone or in small numbers. They are not aggressive but their nervous darting can stress out more sedate tank mates.
- Dieta
- Herbivore
- They are primarily herbivores and will enthusiastically consume almost all types of aquatic plants in an aquarium. Their diet should be rich in high-quality vegetable flakes, spirulina, and fresh greens like romaine lettuce or cucumber. Providing occasional meaty treats like bloodworms is acceptable but should not form the bulk of their meals.
- Expectativa de vida
- 10-15 years
- Tamanho adulto
- 15 cm
- Proporção sexual
- School
- Sex ratio is generally not a significant concern for this schooling species outside of active breeding setups. It is more important to keep them in a sizable school of at least six individuals to reduce stress and skittishness. Males can be distinguished by a slightly longer anal fin tinged with red.
- Frequência de alimentação
- Twice daily
- Silver Dollars should be fed two to three times a day in portions they can consume within a few minutes. Their fast metabolism and active nature require consistent caloric intake. Supplementing their diet with constantly available greens like blanched spinach helps satiate their constant grazing behavior.
- Carga biológica
- Medium to High
- Silver Dollars produce a substantial bioload due to their large size and messy eating habits. They are schooling fish that require spacious aquariums, meaning the cumulative waste output is significant. Heavy filtration and regular, large water changes are necessary to prevent the accumulation of toxic compounds.
- Fluxo
- Strong
- They are accustomed to the moderate currents of South American river basins and appreciate a decent water flow. A good current will encourage their natural schooling behavior and keep them active. Ensure the flow is not so strong that it exhausts them, providing calmer resting areas in the tank.
- Risco de salto
- Yes
- These fish are extremely skittish and prone to panicking, making them a very high jump risk. Any sudden movements or turning on bright lights can cause them to dart to the surface and jump. A tight-fitting, secure, and robust lid is absolutely mandatory for their safety.
- Reprodução
- Oviparous
- They are egg scatterers and do not provide any parental care for their young. In a dedicated breeding tank, females will release thousands of eggs among fine-leaved plants or a spawning mop. The parents must be removed immediately after spawning to prevent them from eating the eggs.
- Compatibilidade e companheiros de tanque
- Highly aggressive
- They are generally peaceful schooling fish that do well in large community setups. However, their size can be intimidating to very small tank mates, and they may occasionally nip at much smaller fish if underfed. Excellent companions include other large tetras, peaceful cichlids, and sizeable catfish.
- Nível do tanque
- Top/Middle
- Silver Dollars are highly active swimmers that primarily occupy the middle and upper levels of the water column. They need plenty of open swimming space to accommodate their size and active schooling behavior. They rarely venture to the bottom substrate unless searching for sunken food.
Modelos e parâmetros científicos
FishBase
Acesso aos dados científicos oficiais da espécie
FishBase v25.04Dados sincronizados em: 15/06/2026
- Nível trófico
- 3,4 ± 0,6 se
- Resiliência
- Alta (menos de 15 meses)
- Unicidade filogenética (PD50)
- 0.5001
- Relação bayesiana comprimento-peso
- a = 0.02754, b = 3.11
- VulnerabilidadeVulnerabilidade baixa (10 / 100)
Espécies relacionadas
Recomendações agrupadas por parentes próximos, escolhas de acompanhantes e cuidados semelhantes.
