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Characins
/ Serrasalminae / Silver Dollar
Silver Dollar
Metynnis argenteus | Pictures
Synonyms: Metynnis
anisurus, M. dungerni, M. eigenmanni, M. heinrothi, Myletes argenteus
Physical description: A tall, laterally compressed fish that is shaped like a disk or plate. It has small
eyes and a back. The base body color is silver and the fins are transparent. The belly is slightly reddish silver.
A line extends through the iris. The pectoral fins are red. A string of spots extends across the body.
Size/Length: To 8" (20 cm)
Similar species: Other Metynnis
species, and fish of the genera
Myletes,
Mylossoma, and
Serrasalmus.
Habitat: South America; shallow areas of rivers with heavy vegetation in Guyana
S: middle
Aquarium: 48" (122 cm) or 55 gallons (210 L) is adequate for smaller fish.
Adult
fish should be moved to a tank measuring at least 56" (142 cm) with a capacity of at least 75 gallons (285 L).
The
tank should be large and roomy with lots of open swimming areas.
Provide hiding places with solid rock structures
and driftwood.
The lighting should be dimmed and use a dark gravel bottom.
Live plants will usually be consumed,
so use plastic plants as an alternative.
Some robust, sturdy plants may not be bothered if the fish are fed
sufficiently.
Silver Dollars prefer shallow tanks.
Water chemistry: pH 6-7.5 (6.8), 4-18 dH (12), 75-82°F (24-28°C)
Social behavior: Keep with fish of relative size, as smaller fish may be eaten.
The Silver Dollar does best when kept
in a school of six or more fish.
Suggested companions: Other "Silver Dollars" (see "Remarks"), Loricarids, Pimelodids, South and Central American
cichlids, Pacus, Arawana, Anostomus.
FOOD: Pellets; vegetables; lettuce, peas, spinach; plants; large vegetable flakes; live
foods are usually accepted.
SEX: Male has a longer anal fin and has a red marking and front of belly.
Breeding techniques: Only possible in a large, shallow tank.
Silver Dollars often spawn in schools.
Recommend water with the following values: a pH 6.0-6.5, a water hardness of 4-8 dH, and a water temperature of
79-82°F (27-28°C).
Have floating plants and slightly dimmed light. About 2000 eggs are produced by each female.
The eggs fall to the bottom.
Remove the adult fish after the spawning.
The fry hatch in 3 days, and are free
swimming after 6-9 days.
They first eat plankton, but later, will take vegetable flakes.
Breeding potential: 9.
Breeding is difficult because of the volume of water needed for a group of fish to spawn.
Remarks: Over 20 species of
Metynnis are available, with most species reaching
about 8" (20 cm) in size.
"Silver Dollars" sometimes include other genera including
Mylossoma and
Myleus.
These genera are difficult to distinguish,
although differences are usually apparent in the adipose fin.
Metynnis
have a long-based adipose fin, while
Mylossoma and
Myleus have a short-based, rounded adipose.
An
important food fish in South America.
Difficulty of care: 5.
The Silver Dollar is a hardy fish that, because of its size, must be kept in a large tank.
Recent articles about fish
Overfishing may hurt Amazon forest trees
(2/5/2008) Overfishing is reducing the effectiveness of seed dispersal by fish in the Brazilian Pantanal, reports Nature. The research suggests that fishing practices can affect forest health.
Scientists find fish that literally lives in trees
(10/17/2007) Scientists have found a fish that literally lives in trees, according to research published in The American Naturalist and highlighted in New Scientist Magazine.
Piranhas originated when Amazon was flooded by seawater
(12/4/2007) South America's piranha family of fish -- notorious as eaters of flesh -- can be traced back to a single ancestor which dispersed when the Amazon was flooded by seawater some five million years ago, report researchers from the Institut de Recherche Pour le Developpement (IRD). Today piranhas are exclusively freshwater fish found from the Orinoco River basin in Venezuela to the Parana in Argentina.
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