At a glance the quick version
Looks how to spot one
Disc-shaped serrasalmid (pacu and piranha family)
A round, very flat-sided fish that looks like a shiny coin. The body is plain silver, sometimes with a hint of red in the fins and throat. Males grow a longer anal fin, often edged red, and show dark spots and stronger colour when breeding.23
Personality what they are like
A peaceful, sociable shoaling fish. In a group with space and cover it is confident; kept alone or in bare tanks it becomes nervous.23
Daily activity how busy a day looks
An active swimmer of the middle and upper water; needs a long tank.3
Grooming and care the hands-on bits
Eats most plants, so choose tough or artificial plants and decor; keep water clean with regular partial changes.3
Home where they are happiest
A large tank for a group, at least 180 x 38 x 38 cm (about 260 litres). Water 24-28 C, pH 5.0-7.0, soft water up to about 10-15 dGH.31
Food basics what goes in the bowl
Mainly herbivorous. Feed plenty of vegetables such as courgette, cucumber, peas and leafy greens, plus algae wafers and spirulina or vegetable flakes, with occasional bloodworm or brine shrimp.32
Company who they like around
Keep at least five together. Good companions are larger peaceful fish and bottom-dwellers like plecos; very small fish may be eaten.3
The story where it all began
The silver dollar was described by German zoologist Christoph Ahl in 1923. It became a popular aquarium fish, especially in the USA, although some older trade records may have mixed it up with the similar Metynnis hypsauchen.21
Fun facts for the dinner table
- 1
It is a close relative of piranhas but feeds mostly on plants.3
- 2
Silver dollars spawn in groups and scatter their eggs; breeders sometimes cover the tank floor with marbles so eggs fall out of reach.2
- 3
It can be told apart from the similar Metynnis hypsauchen by the lack of a dark blotch above the eye.3
- 4
In the wild it lives in weedy side channels of the river.1
Recognised by the official bits
- IUCN Red List
- Assessed as Least Concern (October 2020)1
- FishBase
- Listed as commercially important in the aquarium trade and minor fisheries1
The care rhythm a typical week and year
A typical home-care rhythm for a Silver Dollar. A starting point, not a vet's advice.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
Owner questions the things everyone asks
How often should I feed my Silver Dollar?
Feed your Silver Dollar small amounts once or twice a day. Furry Diary's starting plan is to feed daily, but always check the food label and ask your vet for exact portions.3 Pet Wiki plan
What does a Silver Dollar eat, and what should it never eat?
Silver Dollars are mainly herbivorous and enjoy vegetables like courgette, cucumber, peas, and leafy greens, plus algae wafers and spirulina flakes, with occasional bloodworm or brine shrimp. They should never be fed foods that are not plant-based or appropriate for their diet, and avoid overfeeding.32
How much space does a Silver Dollar need?
A group of Silver Dollars needs a large tank, at least 180 x 38 x 38 cm (about 260 litres). They are active swimmers and need a long tank to thrive.31
What temperature, light or water does a Silver Dollar need?
Keep the water temperature between 24-28°C, pH 5.0-7.0, and soft water up to about 10-15 dGH. They need a well-planted tank with tough plants or artificial decor, as they eat most plants.31
How often should I clean a Silver Dollar's home?
Furry Diary's starting plan is to do a 25% water change weekly, test the water weekly, clean the glass weekly, and rinse the filter in old tank water monthly. Always use dechlorinated water. Pet Wiki plan
Can a Silver Dollar live with others?
Yes, Silver Dollars are peaceful shoaling fish and should be kept in groups of at least five. Good companions are larger peaceful fish and bottom-dwellers like plecos, but very small fish may be eaten.3
How long does a Silver Dollar live?
The lifespan of a Silver Dollar varies depending on care and environment. For specific information, ask a good breeder or an exotic-pet vet.
Can I handle a Silver Dollar?
No, you should not handle a Silver Dollar. They are delicate fish and handling can cause stress or injury. Always use a net if needed and keep them in water.3
Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Pet Wiki's own starting care plan. A friendly guide, not a vet's advice.
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Red-bellied PiranhaWhere this comes from
Every fact on this page has a numbered source. Spotted an error? support@petwiki.app.
- Metynnis argenteus, FishBase fishbase.seused for distribution, max length and weight, water parameters, IUCN status, habitat, author
- Metynnis argenteus, Wikipedia en.wikipedia.orgused for size, colours, history, behaviour, breeding
- Metynnis argenteus, Seriously Fish seriouslyfish.comused for origin, size, tank and water parameters, diet, behaviour, appearance
Checked 2026-09-30. Text is written in our own words from these sources.