Silver Dollar

With its laterally compressed, almost round silver body, the silver dollar resembles a coin. It belongs to the same family as piranhas and pacus, but its teeth are suited to tearing off plants and its diet is largely plant-based. Fish sold in the trade as "silver dollars" can belong to several different Metynnis species; their care is very similar.

It is a schooling species that reaches 14–15 cm. The small juveniles seen in stores grow quickly; a large aquarium should be planned from the start.

It lives in schools in densely vegetated, slow-flowing river branches and floodplain lakes of the Amazon basin. The water is soft and slightly acidic; during the flood season it feeds on plants and fruit in the flooded forest.

• Volume: at least 300 liters for a group of 5–8; a length of 120 cm or more.
• Water: 24–28°C, pH 6–7.5, soft to moderately hard water.
• Plants: most live plants get eaten; even hard-leaved species such as Anubias and Java fern can be damaged. It is more practical to set up the decor with roots, stones and artificial plants.
• Lid: it jumps powerfully when startled; a lid is needed.
• Filter: because it eats a lot, strong filtration and a 30% water change every week are recommended.

Mainly herbivorous. Make flakes and granules with spirulina and plant ingredients the staple. Blanched spinach, lettuce, zucchini, cucumber slices and peas are eaten eagerly. Protein sources such as frozen bloodworms or mysis shrimp can be added a few times a week.

A peaceful and skittish species. It swims in a school in the middle water and flees together at sudden movements. It does not attack other fish but may eat small shrimp and very small fry that fit in its mouth.

Good companions: large, peaceful species: large plecos, large corydoras, Congo tetras, peaceful medium to large cichlids such as severums and geophagus, kissing gouramis.

Avoid: dwarf shrimp, nano fish, planted aquariums, aggressive large cichlids.

It is a schooling fish: at least 5, ideally 8 individuals. Fish kept alone or in pairs become extremely skittish and hide constantly. The sex ratio does not matter.

It is an egg scatterer. In large, mature aquariums pairs sometimes spawn on their own; the eggs scatter among plants or onto the bottom. There is no parental care, and other fish eat the eggs. The fry become free-swimming after a few days and are fed fine powdered food.

• White spot (ich): may appear after transport; quarantine is recommended.
• Water quality: a large, heavy-eating school increases the waste load; keep nitrate low.
• Injury: it may crash into the glass and decor when fleeing suddenly; a calm room and steady lighting help.

Males have a longer anal fin whose front part is lobed and has a reddish or dark edge. Females have a straight-edged anal fin and slightly plumper bodies.