Home / Fishes / Tetras, piranhas and pacus / Metynnis argenteus
No federal permit to keepMetynnis argenteus
Metynnis argenteus
Fishes › Tetras, piranhas and pacus (Characiformes) › Serrasalmidae (Piranhas and pacus)
Metynnis argenteus is a species of freshwater ray-finned fishes belonging to the family Serrasalmidae, which includes the pacus, piranhas and related fishes.
Care at a glance
Species-specific aquarium care
- Tank: At least 36 in long and 12 in front to back for one adult (adults commonly reach about 5.5 in / 13.96 cm).
- Water: Freshwater.
- Temperature: 75–82°F (range recorded for this species).
- pH: 5–7.
- Hardness: 0–15 dGH.
- Layout: An open-water swimmer: needs long, open swimming space with few obstacles.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 71 × 15 in (roughly 69 US gallons); space needed is rated “very large tank”.
- Water: soft, acidic water, 75–82 °F, pH 6–7, 0–10 dGH.
- Behaviour: temperament predatory; a shoaling fish best kept in a group of six or more.
- Difficulty: Difficult (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “Silver dollars inhabit densely planted river tributaries in the wild.”
- Diet: “Provide a large amount of vegetable matter in the diet, including; courgette, cucumber, peas, spring greens and other green vegetables.”
- Tankmates: “Best kept in groups of at least five fish.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Piranhas, pacus and silver dollars
Applies to most species in this group. Habitat: South American rivers. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- Large tanks with strong filtration; pacus grow to over 2 ft and outgrow almost every home aquarium.
Diet
- Silver dollars: plant-based foods. Piranhas: fish, shrimp and pellets.
Health watch
- Piranhas are banned in many states. Never release pacus.
Understanding the animal
About this animal
About this animal
This fish is endemic to the Tapajós River Basin in Brazil. It is one of the species known in the aquarium trade as the "silver dollar".
Quoted from the Wikipedia article “Metynnis argenteus” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater. In weedy side arms of the river; popular aquarium fish in the USA according to, but might be a misidentification of M. hypsauchen. Needs better reference. |
| Water it lives in | Freshwater, 75–82 °F (24–28 °C), pH 5–7, hardness 15 dH. |
| Climate | Tropical climate. |
| Behavior to plan for | Breeding: open water/substratum egg scatterers. |
What this means for care
- Keep water within its wild range, 75–82 °F.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 92°F (up to 95°F in the hottest sampled areas) |
| Cool-season lows | about 71°F (down to 68°F in the coldest sampled areas) |
| Average temperature | 79–82°F across sampled records |
| Relative humidity | 75–82% on average (driest month about 67%) |
| Rainfall | about 2178 mm a year |
Measured at 87 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | Metynnis argenteus is a species of freshwater ray-finned fishes belonging to the family Serrasalmidae, which includes the pacus, piranhas and related fishes. This fish is endemic to the Tapajós River Basin in Brazil. It is one of the species known in the aquarium trade as the "silver dollar". M. argenteus is generally considered the archetypal silver dollar, although it and the very similar M. hypsauchen frequently have been confused. — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Wild diet | Metynnis argenteus, like all other known Metynnis, are mainly herbivores, but also take animal matter. They will readily and eagerly accept dried flake food as well as live and frozen foods like bloodworm, shelled shrimps, rinsed tuna, daphnia and brine shrimp. Their diet should be varied to keep them in good condition. — Wikipedia (community-edited) |
| Behavior | A very peaceful shoaling species, M. argenteus can be skittish and timid if left without any kind of shelter, and if kept in isolation they tend to become reclusive. Kept in a shoal, given plenty of room to move and provided with cover behind which they can hide if they feel threatened, they do very well indeed. — Wikipedia (community-edited) |
| Reproduction | Assumed to be like Metynnis hypsauchen. — FishBase |
| Biology | In weedy side arms of the river; popular aquarium fish in the USA according to, but might be a misidentification of M. hypsauchen. — FishBase |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Typical adult weight
Average adult body mass in each database (FishBase gives the maximum recorded weight).
Adult length
Maximum recorded length. Measured as standard length (snout to the base of the tail, not counting the tail fin). Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Water hardness
Minimum tank footprint
Seriously Fish recommends a tank base of at least 71 × 15 in (about 69 US gallons).
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Merck Veterinary Manual: Management of aquarium fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Types and features of aquatic systems Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Nutritional diseases of fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
- iNaturalist (captive observations) Community referenceCommunity observation platform run by the California Academy of Sciences and National Geographic; observations marked captive show animals living in homes, zoos and aquariums.
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