Silver Dollar
Metynnis hypsauchen
Serrasalmidae
No photo of this species yet
Got one of your own? Send it and your name goes under it.
About
The silver dollar is a piranha relative that went vegetarian, and it is sold at coin size to people planning a planted community tank. Both halves of that sentence cause trouble. On size: Seriously Fish gives 15 cm standard length, FishBase records 18 cm SL and Maidenhead Aquatics quotes 20 cm, and it is a disc — a fully grown fish is roughly as deep as it is long, so six of them are a wall of fish, not a shoal of tetras. On plants: this is one of the few aquarium fish where the plant warning is not a myth. Seriously Fish calls it 'an avid plant-eater' whose hardy plants 'will still need to be replaced regularly'; Maidenhead says 'They will devour most plant species in their aquarium' and suggests silk substitutes; AquaInfo states that 'since they are large herbivores, plants cannot be used as decoration' and that in the wild they eat from the leaves of aquatic plants. Three independent sources, all about living plants, all about this species. It is otherwise a genuinely peaceful, nervous, fast-moving shoaler — but FishBase notes it 'possesses powerful dentition that can cause serious bites', and Seriously Fish warns that much smaller fish may be eaten.
Care
Six minimum, and a big tank. Seriously Fish puts a group of adults at 180 x 37.5 x 37.5 cm (265 litres); Maidenhead says juveniles need four feet and adults an aquarium of at least six by two by two feet, which is around 650 litres. Our gate sits at the low end of that: 180 cm long, 45 cm front to back and 45 cm tall, 300 litres. The height is a requirement in its own right — a fish this deep in the body needs it — even though Seriously Fish says length and width matter more than height and specifies a 37.5 cm-tall tank. Subdued lighting, a quiet spot away from foot traffic, and no sharp decor — these fish bolt when startled and injure themselves on it. Tight coverslides: they jump. Water 24-28 C, pH 6-7.5, soft to moderately hard, well filtered, well oxygenated, with real flow and low nitrate. Plan the planting as consumable or use hardscape and epiphytes: Java fern and Anubias sometimes survive, everything softer does not. Tankmates must be too big to swallow and calm enough not to spook the group; large peaceful catfish work well.
Diet
Herbivore. Vegetables and algae-based dry foods should form the bulk — courgette, cucumber, peas, spring greens, spinach, algae wafers, Spirulina flake — with frozen bloodworm or brine shrimp as an occasional extra. Feeding greens well does not make it plant-safe; it makes it slower to strip the tank.
Tankmate compatibility
Gets along with (139)
Possible with care (216)
Avoid (63)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
There is no reliable way to sex this species by eye. That is the honest answer, not a gap in our data.
All the methods, with diagramsSimilar species
Same category and the closest water parameters — if this species isn't quite it, start here.
Sold in Lithuania
These Lithuanian shops listed this species in their public catalogue (checked August 8, 2026). Stock moves — ask before you travel.
These links are unpaid: we get nothing for them and ask for nothing.
Frequently asked questions
- What tank size does a Silver Dollar need?
- A Silver Dollar needs an aquarium of at least 300 litres (79.3 US gallons) with a footprint at least 180 cm (70.9 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Silver Dollar need?
- Silver Dollar does best at 24–28 °C (75.2–82.4 °F), pH 6–7.5 and a general hardness of 2–12 °dGH.
- What group size does a Silver Dollar need?
- Silver Dollar is a social species — keep a group of at least 6 so natural behaviour emerges and stress stays low.
- Is the Silver Dollar suitable for beginners?
- Silver Dollar sits in the middle of the difficulty scale — manageable for a careful beginner who has done the reading, but it has specific needs worth researching first.