Metynnis: Greek, meta = with, after + Greek, ynnis, -eos = ploughshare
A medium sized fish which is very lively and so needs more space than its size leads you to believe. As the fish grow they become increasingly wary and are prone to panic if they are startled. They should be kept in a group of at least five individuals, with other small to medium sized peaceful fish which will help to reassure them. Very small fish like tetras may be eaten though. In the wild silver dollars come from areas with dense vegetation, this isn't possible to replicate in captivity due to their plant eating, but one aspect of dense vegetation is subdued lighting as a result silver dollars are less nervous under dim lighting than in brightly lit tanks. Silver dollars although herbivores are close relatives of the piranha, they have a very powerful bite and relatively strong teeth so be careful when handling large adults.
Silver dollars are herbivores, they will eat all aquatic plants so if you want to include some plants in their aquarium they will have to be artificial. Feeding silver dollars isn't as straight forward as just using a commercially prepared dried food if they are to remain healthy. Lots of fresh greens must make up the bulk of their diet - lettuce, water cress, blanched spinach, cucumber, skinned processed peas, algae wafers and occasionally live or frozen food once or twice per week. Being herbivores they prefer to constantly graze so feeding should be little and often.
The difference between the sexes is slight, the males anal fin is elongated and more colourful than that of the female in healthy adult fish.
Silver dollars have been bred in captivity many times, a healthy pair or group may spawn in a community tank with no encouragement if they are healthy and well cared for. But it is always better to use a specially prepared spawning tank so that the adults can be removed after spawning and the fry can then be allowed to grow up in safety. Raising the temperature by a few degrees and feeding a diet which is higher in protein than their usual diet with more live or frozen food will help to bring them in to spawning condition. Silver dollars will spawn as a pair or as a group with each female producing up to 2,000 eggs. The fry are very tiny and once free swimming they will eat infusoria or a commercial liquid fry food until they are big enough to move on to other types of food.
Metynnis hypsauchen is a widespread species which can double its wild population in 15 months and so it faces no immediate threats.
pH: 6 - 7
dGH: 4 - 15
Temperature: 24 - 28°C (75 - 82°F)
Size: 15cm (6in)
Min tank size: 450 litres
Difficulty level: Intermediate
Aquarium type: Community
Swimming level: All levels
Origin: South America: Amazon and Paraguay River basins, north Guiana Shield rivers.
Habitat: Inland river basins and tributaries.
Species: M. hypsauchen. (Müller Troschel, 1844)
Synonyms: Myletes hypsauchen, Metynnis schreitmuelleri, Metynnis ehrhardti, Metynnis calichromus schreitmuelleri Metynnis calichromus