Silver Dollar Fish – Metynnis sp. 5cm

The Silver Dollar Fish – Metynnis sp. is a distinctive South American tropical fish recognised for its round, laterally compressed body and bright metallic silver colour.

Silver Dollars are active, social fish that are best kept in a group. Their schooling behaviour and reflective silver bodies make them particularly impressive in larger freshwater aquariums with plenty of open swimming space.

Fish supplied are approximately 5cm unless otherwise stated.

Please note: several closely related Metynnis species are sold in the aquarium trade under the common name Silver Dollar. Unless the exact species has been confirmed by the supplier, we recommend referring to these fish as Metynnis sp. rather than assigning a species name based on appearance alone.

Fish Profile

• Common Name: Silver Dollar Fish
• Scientific Name: Metynnis sp.
• Family: Serrasalmidae
• Sale Size: Approximately 5cm
• Adult Size: Approximately 15–18cm depending on species
• Origin: South America
• Temperament: Generally peaceful
• Social Behaviour: Shoaling; keep in a group
• Recommended Group Size: At least 5
• Temperature: Approximately 24–28°C
• pH: Approximately 6.0–7.0
• Water: Soft to moderately hard freshwater
• Recommended Aquarium: Around 260 litres or larger for an adult group
• Diet: Omnivorous with a strong plant-based component
• Swimming Level: Mid to upper water

About Silver Dollar Fish

Silver Dollars belong to the family Serrasalmidae, making them relatives of piranhas and pacus, although their behaviour and diet are very different from the predatory reputation often associated with that family.

Their deep, disc-shaped bodies give them the appearance of a large silver coin, which is where the common name comes from.

Several species within the genus Metynnis are sold as Silver Dollars. Two of the most frequently confused are Metynnis argenteus and Metynnis hypsauchen. Their aquarium requirements are very similar, which is why the general care information below is suitable for the common Silver Dollars encountered in the aquarium trade.

How Big Do Silver Dollars Grow?

Silver Dollars sold at around 5cm are still juveniles.

Depending on the exact species, adults can reach approximately 15–18cm.

They are also deep-bodied and highly active swimmers, so aquarium length and open swimming room are particularly important.

For an adult group, an aquarium around 180cm long and approximately 260 litres or larger is a sensible minimum target.

Silver Dollars Need to Be Kept in a Group

Silver Dollars are naturally social fish and should not normally be kept individually.

A group of at least five Silver Dollars is recommended. Keeping them in an appropriate group helps the fish display more natural behaviour and generally improves their confidence.

Because an adult group needs considerable swimming room, plan the aquarium around the eventual adult size of all the fish rather than their 5cm purchase size.

Aquarium Setup

Silver Dollars are active midwater swimmers and need plenty of open space.

A suitable aquarium can include:

• Large open swimming areas
• Driftwood
• Rockwork positioned around the edges
• Shaded or sheltered areas
• Strong, reliable filtration
• Good water quality

Silver Dollars can initially be nervous or skittish, so areas of cover and a well-structured aquarium can help them feel secure.

Can Silver Dollars Be Kept With Live Plants?

Silver Dollars are enthusiastic plant eaters.

Although they naturally occur around aquatic vegetation, many aquarium plants may be eaten or damaged when kept with a group of Silver Dollars.

If you want a heavily planted display aquarium, Silver Dollars may not be the best choice.

Hardy plants may sometimes survive, but even robust species can be sampled. Driftwood, rocks and artificial plants are often more practical for creating cover without constantly replacing eaten plants.

Water Conditions

Silver Dollars prefer warm, clean freshwater with stable conditions.

• Temperature: Approximately 24–28°C
• pH: Approximately 6.0–7.0
• Hardness: Soft to moderately hard water

Regular partial water changes and appropriately sized filtration are important because a mature group represents a significant aquarium bioload.

Feeding Silver Dollar Fish

Silver Dollars are omnivorous but consume a substantial amount of plant material.

Their aquarium diet should contain plenty of vegetable-based foods rather than relying entirely on high-protein tropical fish foods.

Suitable foods can include:

• Spirulina flakes
• Vegetable-based pellets
• Algae wafers
• Suitable leafy greens
• Zucchini or courgette
• Cucumber
• Quality tropical flakes and pellets
• Occasional brine shrimp or bloodworm

A varied diet with a strong vegetable component helps better reflect their natural feeding behaviour.

Browse our aquarium fish food range for suitable tropical and vegetable-based foods.

Temperament and Tank Mates

Silver Dollars are generally peaceful community fish when housed with suitable tank mates.

However, their adult size means very small fish may not be appropriate companions.

Suitable tank mates can include larger peaceful tropical fish, appropriately sized catfish and other species that prefer similar water conditions.

Avoid housing Silver Dollars with very small fish that could potentially be eaten, or with highly aggressive species that continually harass them.

Are Silver Dollars Suitable With Oscars?

Silver Dollars are sometimes maintained alongside Oscars and other large South American cichlids because their speed, adult size and group behaviour can make them more suitable than small community fish.

Compatibility is never guaranteed. The aquarium must be sufficiently large and individual fish temperament should always be considered.

Why Choose Silver Dollar Fish?

Silver Dollars are an excellent choice for aquarists looking for a larger, peaceful schooling fish.

Their reflective silver colour, unusual disc-shaped body and coordinated group movement create an impressive display in a spacious freshwater aquarium.

They are particularly well suited to larger South American-style aquariums where open swimming space is prioritised over delicate live plants.

Browse more Tropical Freshwater Fish available from Aquaholics.

Frequently Asked Questions

How big do Silver Dollar Fish grow?

Depending on the exact species, Silver Dollars commonly grow to approximately 15–18cm and develop a deep, disc-shaped adult body.

How many Silver Dollars should I keep together?

Silver Dollars are social shoaling fish and should generally be kept in groups of at least five.

What size aquarium do Silver Dollars need?

An adult group requires a large aquarium with substantial horizontal swimming space. Around 180cm in length and approximately 260 litres or larger is a sensible minimum target for a group.

What temperature do Silver Dollars need?

A temperature of approximately 24–28°C is suitable for commonly kept Silver Dollar species.

What pH do Silver Dollar Fish prefer?

A pH of approximately 6.0–7.0 is suitable for commonly kept Metynnis Silver Dollars.

Are Silver Dollars peaceful?

Yes. They are generally peaceful fish when maintained in a suitable group with appropriately sized tank mates.

Do Silver Dollar Fish eat aquarium plants?

Yes. Silver Dollars consume significant amounts of plant material and may eat or damage many live aquarium plants.

What do Silver Dollar Fish eat?

They are omnivorous but should receive a diet containing plenty of vegetable matter. Suitable foods include spirulina flakes, vegetable pellets, algae wafers, greens and appropriate tropical fish foods.

Can Silver Dollars live with small fish?

Very small fish may be at risk of being eaten by adult Silver Dollars. Tank mates should be selected according to adult size and compatibility.

Are Silver Dollars related to piranhas?

Yes. Silver Dollars belong to the family Serrasalmidae, which also contains piranhas and pacus, but Silver Dollars are generally peaceful and have very different feeding behaviour.