Silver dollar fish (Metynnis argenteus)

Silver dollars fish (lat. Metynnis argenteus) belongs to Characidae family. In the 19th century in the USA there was a coin of 1$ nominal, so it was noticed that the fish juveniles due to their rounded and flattened body shape really may resemble the coin and their silvery coloring only made the likeness stronger.

Habitat in the wild

The Latin name of the fish “argenteus” itself means covered with silver.

Metynnis argenteus was first described in 1923. The fish inhabits in the Amazon river (South America) – the territory of modern Paraguay and Brazil. Along with this fish kind you can also see Metynnis hypsauchen in tanks. These two fishes are almost identical in their appearance.

Also you may encounter several more kinds of Metynnis on the trade including spotted silver dollar fish – M. lippincottianus. It differs from the previous fish kinds in the numerous rounded gray spots on its body sides.

However, all kinds of Metynnis are alike in their behavior and care. These are schooling fishes, that as a rule inhabit in thickly planted tributaries, where they mainly feed on plant food.

In the wild fish prefers the latter one, however it’ll gladly feed on protein containing feed.


Max size may be up to 8″ (20cm) and its lifespan may be from about 10 years and more.

The body is tall, laterally flattened and it has rounded and rhombic shape. The coloring is silvery, sometimes with bluish or greenish opalescence.

Some species have vertical stripes, but not very pronounced. The fins may be a bit reddish and anal fin of a male is the most brightly colored one.

Difficulties in keeping

Care is rater easy, since the fish is quite strong and not demanding.

It is a large one, so it requires a spacious tank. For the fish owner it’s better to have some experience in keeping some other fish, since for Metynnis school of 4 species a tank from 80 gallons capacity and more is required.

Also, keep in mind that tank plants are just feed for this fish.

Keeping in a tank

Scientific NameMetynnis argenteus
Common NameSilver dollar fish, dollar fish, silver dollar tetra, silver coin fish
Tank size8 gallons (300L) and more
Temperature75–81 °F (24–27 °C)
Size8 inches (20 cm)

Fish is a rather large one and it should be kept in a school of at least 4-5 species that will require a tank of at least 80 gallons capacity.

This fish swims in all water layers and it needs some free space for swimming. Silver dollar fish feels itself more comfortable in a tank with dark bottom and dim lights.

However, it is active and it can jump, so you’ll have to close the tank tightly and fasten all decorations and equipment in the tank.

Metynnis is rather not demanding and is resistant to diseases, also the fish is capable to live in very different tank conditions.

All that is important is clean water, powerful filter and regular water renew. The fish likes moderate water flow as well and it can be created by means of the filter.

Large Metynnis species can start tearing around the tank when scared and it can even break the heater, so you’d better not use the glass ones.

Keep in mind that Metynnis will eat all the plants in your tank, so it’s better to plant some rigid leaved plants, such as Anubias or some kind of plastic plants. Proper water temperature is: 24-27 C, ph: 6.5-7.5, 4 – 18 dGH.


The interesting thing is that, although the Metynnis is Piranha “cousin”, it unlike the latter feeds mainly on plant food. Flakes with spirulina, lettuce, spinach , cucumbers, squashes are among its favorite feed.

So if your fish diet is mainly vegetable, don’t forget to remove the leftovers from the tank, since they make the water muddy.

Though fish diet is a plant one, it’ll eagerly eat protein containing food – blood worm, brine shrimp. In a community tank silver freshwater fish may become rather timid, so make sure that the fish has enough food.

Compatibility and tank mates

Is a peaceful and active one, but it shouldn’t be kept together with fishes of smaller size, since the latter will be attacked and those the smallest ones will become the fish feed.

They should be kept in a school of at least 4-5 species. Tank mates can be the following: bala shark, giant gourami, sailfin pleco and other large fishes including cichlids, like green terror, blue acara and oscar, convict cichlid, Jack Dempsey.

Gender differences: male vs female

Male has a larger anal fin, than the female, and its front section is red colored.


Dollar fish becomes reproductive when it becomes about 1 year old. Before spawning the fishes that are to breed are removed from their school, put apart in different tanks for about 7-10 days and fed well with plant feed.

A spawning tank should be of at least 40 gallons capacity with fresh and soft water, which hardness doesn’t exceed 4°, pH 6,4-7,0 and the water temperature is 26-30 °C.

You should put some plants in the tank and artificial substrate. Female lays about 300-1000 eggs, they are transparent, not sticky and a bit yellowish. The eggs fall on the tank bottom on the plant leaves.

Breeding the fishes should be removed from the tank, though they don’t tend to da any harm to their eggs.

Eggs incubation period will last about 4-6 days. When juveniles start to swim, they can be fed with brine shrimp and cyclops nauplii, small plankton, milled salad leaves and artificial feed as a start feed.

Juveniles provided with good feed at the age of 6-8 month become of the same size as the adult fish.

About author: Sergey Schulz

Sergey is a founder and author of He’s been fond of aquarium husbandry since his early childhood. His favorite aquariums are biotopes (Amazon River), with Echinodorus and freshwater angelfish. However, through the years he’s had experience of keeping almost all types of freshwater fish and shrimps.