Care guide · Freshwater · fish

Silver dollar

Metynnis hypsauchen

No verified species photo available yet

Metynnis hypsauchen is a South American silver dollar in the family Serrasalmidae. In the aquarium trade, ‘silver dollar’ is also used for other Metynnis species, especially M. argenteus. The two look very similar; the specialist profile notes a dark blotch above and behind each eye in M. hypsauchen. Confirm the identity before purchase. This species needs a spacious aquarium, a shoal, and a varied diet that is strongly plant-based. The eye blotch can help with recognition, but ask about provenance and identification whenever the trade label is uncertain.

Plan your aquarium →

At a glance

Temperature: 24–28 °C
pH: 6.0–7.0
GH: 0–10 °dGH
Aquarium length: At least 180 cm
Minimum aquarium volume: At least 260 L
Adult size: Approximately 15–18 cm
Group size: At least 5 individuals
Temperament: Peaceful

About this species

Seriously Fish reports 150 mm standard length, while FishBase lists up to 180 mm standard length. Keep this difference visible: standard length excludes the tail fin and the sources do not report the same maximum. Do not plan only around the lower figure. Adults are deep-bodied and mainly swim in midwater and upper water. A juvenile in a shop is not a reliable indication of adult housing needs.

Natural habitat

Seriously Fish describes a patchy distribution in Guyana, Brazil, Peru and Bolivia, with records from the Amazon and Paraguay drainages and rivers of the Guiana Shield. This is a summary of distribution reports, not a requirement to recreate one exact biotope. In the aquarium it is a tropical freshwater fish. Ecological knowledge about the genus remains partly uncertain.

Aquarium and layout

For an adult group, Seriously Fish recommends a 180 × 38 cm footprint and about 260 litres at the stated tank height. Length and width matter more than extra height. Since FishBase reports a larger maximum length, 260 litres is a specialist-recommended baseline, not a guarantee for every large specimen. Keep at least five fish together, leave ample open swimming room, and use a secure cover.

Water conditions

The specialist aquarium profile gives 24–28°C, pH 6.0–7.0 and GH 0–10 dGH. Set up for stability and avoid rapid or substantial swings. Regular water changes and reliable filtration help control waste. Older ecological data may show broader values, but these are not aquarium recommendations. Measure the water and acclimate new fish gradually to the conditions in which they have been kept.

Behaviour and group size

Keep this silver dollar in a group of at least five. It is generally considered peaceful with larger, calm fish, but much smaller fish may be eaten. Select companions by adult size and activity. The shoal uses midwater and upper water and needs room to swim. They readily eat live plants; subdued lighting and refuge can help nervous fish. The eye blotch is useful for identification but does not replace reliable provenance.

Feeding

Metynnis hypsauchen eats a strongly plant-based diet, while accepting a range of foods. Offer variety with suitable vegetables and complete vegetable foods such as spirulina or algae-based diets. Small animal foods can be occasional supplements. Check that every fish feeds, particularly after introduction. Remove leftovers promptly and avoid relying on protein-heavy animal foods; plant matter should make up most of the diet.

Breeding

The specialist profile describes group spawning in a large breeding aquarium. Eggs fall to the bottom and are reported to hatch in around three days; after absorbing the yolk sac, fry need very fine food such as infusoria. These are source descriptions, not a guaranteed breeding method. Provide sufficient breeding space and plan for raising fry. Also account for identification confusion within the genus.

Sources & review

This care guide draws on several specialist sources and was last checked on 16 October 2026.

View the sources