Silver Dollar

Also known as: Metynnis argenteus

The Silver Dollar (Metynnis argenteus) is a laterally compressed, disc-shaped characin known for its shiny, silvery scales that resemble a silver coin. The Silver Dollar originates from Amazon River basin in South America, including Brazil, Peru, and Bolivia, reaches 15 cm in captivity, typically lives 8-10 years, and is kept at 24-28°C (75-82°F). Individual fish vary, so treat this as a general guide rather than a guarantee.

Species at a glance

Origin: Amazon River basin in South America, including Brazil, Peru, and Bolivia
Adult size: 15 cm (6 inches)
Life span: 8-10 years
Temperament: Peaceful and schooling; best kept in groups of 6 or more
Tank size: 150 liters (40 gallons) minimum for a group of 6
Water temp: 24-28°C (75-82°F)
pH range: 6.0-7.5
Diet: Omnivorous; primarily herbivorous, feeding on algae, plant matter, and supplemented with high-quality flakes, pellets, and occasional blanched vegetables like zucchini or spinach
Other names: Metynnis argenteus

About the Silver Dollar

The Silver Dollar (Metynnis argenteus) is a laterally compressed, disc-shaped characin known for its shiny, silvery scales that resemble a silver coin. Native to slow-moving, vegetated waters of the Amazon basin, it thrives in well-planted aquariums with open swimming spaces. This species is peaceful and highly social, exhibiting natural schooling behavior when kept in adequate numbers. Its active nature and striking appearance make it a popular choice for community tanks with similarly sized, non-aggressive fish.

Lifespan and health

With proper care, Silver Dollars typically live 8-10 years in captivity, though exceptional individuals may reach 12 years under optimal conditions. Longevity is strongly influenced by diet quality, water stability, and stress reduction; consistent vegetable-based nutrition and low-stress schooling environments significantly extend lifespan. Regular monitoring of weight and activity levels helps detect early signs of decline, as sudden lethargy or loss of appetite often precedes health issues. Common health problems include bacterial infections (such as fin rot or ulcer disease) triggered by poor water quality, particularly when ammonia or nitrite spikes occur; parasitic infestations like ich (white spot disease) are also possible, especially in newly introduced fish or during temperature fluctuations. Digestive disorders, including bloating or constipation, can arise from excessive protein or insufficient fiber in the diet, emphasizing the need for a predominantly plant-based regimen. Preventative care includes quarantining new fish for 2-4 weeks, maintaining nitrate below 20 ppm, and providing ample vegetation to support natural grazing behavior and reduce stress.

Overview

Care and tank setup

Silver Dollars require a spacious aquarium of at least 150 liters (40 gallons) for a group of six, with larger tanks (200+ liters/50+ gallons) recommended for long-term health and natural behavior. The tank should be well-planted with hardy species like Java fern or Anubias, as they may nibble on softer plants, and include driftwood and rocks for shelter while maintaining open central swimming areas. A sandy or fine gravel substrate mimics their natural riverbed environment. Water conditions must be stable: maintain temperature between 24-28°C (75-82°F), pH 6.0-7.5, and hardness of 5-15 dGH. Use a efficient filtration system to handle their moderate bioload and perform 25% weekly water changes to keep nitrate levels below 20 ppm. Feed a varied diet twice daily, offering only what they can consume in 2-3 minutes; prioritize vegetable-based foods (spirulina flakes, blanched lettuce, cucumber) and supplement with protein-rich foods like bloodworms or brine shrimp 2-3 times per week. Avoid overfeeding to prevent digestive issues and water quality degradation. Ideal tankmates include other peaceful, similarly sized characins such as tetras, rasboras, or Corydoras catfish; avoid aggressive cichlids or fin-nippers like tiger barbs, and never house with small fish that may be seen as prey due to their active foraging behavior.

Adding a Silver Dollar? Research the species’ adult size and temperament carefully, quarantine new fish before introducing them to your tank, and buy from reputable aquarium stores or breeders.

Breed information on this page is based on the Wikipedia article on the Silver Dollar, supplemented with additional research. Reviewed for accuracy.