The Silver Dollar Fish Metynnis argenteus looks just as its name implies, round and silvery. This characin is called “Silver Dollar” because its body is almost round and very compressed laterally. The scientific name says it all: the genus term Metynnis means “with plowshare,” and the species name argenteus means”covered with silver”.

M. argenteus characins are generally a silver color, but with slight green and blue tints in the right light. Hints of red will also appear, especially on the anal fin of the male, which is edged in red. In some habitats, they will have small dots on their sides.

This species and its close relative Metynnis hypsauchen are both known as Silver Dollar. These fish are virtually identical in both looks and aquarium care, and both are commonly available. The two species can only be distinguished by the black blotch or shoulder patch found slightly above and behind each eye on the M. hypsauchen.

The Silver Dollar, though very peaceful, gets rather large and needs plenty of room. It is fairly hardy and makes is a great choice for an intermediate aquarist who wants a community aquarium with good-sized inhabitants. Juveniles can be kept in a 4-foot (122 cm), 50 to 55 gallon (190 – 208 L) aquarium, but adults need 75 gallons (284 L) or more.

These fish are happiest in a large, shallow aquarium with peat-filtered water, dark gravel, and lots of plants and hiding places. The Silver Dollar does like to eat plants, so get plants that are not so tasty, like java fern and hornwort, or you can use artificial plants. These lively fish like to hang out in schools in a tank that provides lots of places for retreat. To be content, they need to be kept in groups of 5 or more individuals. They are skittish fish, and when kept singly and without any hiding places, can become reclusive.

Scientific Classification


Silver Dollar Fish – Quick Aquarium Care

Aquarist Experience Level:Intermediate
Aquarium Hardiness:Moderately hardy
Minimum Tank Size:75 gal (284 L)
Size of fish – inches5.9 inches (15.01 cm)
Temperature:75.0 to 82.0° F (23.9 to 27.8&deg C)

Habitat: Distribution / Background

The Silver Dollar Metynnis argenteus was described by Ahl in 1923. This species is not listed on the IUCN Red List. They are found in South America, though reports about their habitats are inconclusive. Atlas references indicate that they are found in Guyana, the Amazon east of Rio Negro to Paraguay, but this may actually refer to the occurrence of its close relative Metynnis hypsauchen, also known as the Silver Dollar Fish. Other sources suggest M. argenteus is possibly endemic to the Tapajós River basin in Brazil.

A number of fish are known by the common name Silver Dollar. Most are members of the Metynnis genus, which contains 14 described species, and the Myloplus genus with only 2 described species. However, M. argenteus and M. hypsauchen are the two species generally referred to simply by this common name. Most of the other species have other qualifiers to their names, like the frequently encountered Red Hook Silver Dollar Myloplus rubripinnis, the Striped Silver Dollar M. fasciatus (and sometimes M. guaporensis), the Spotted Silver Dollar M. lippincottianus, Red-spot silver dollar M. luna, Speckled Silver Dollar M. maculatus, Black-barred Silver Dollar M. otuquensis, and others.

This schooling species mostly inhabits small, heavily-grown tributaries where it feeds primarily on vegetable matter. They are normally herbivores in the wild but will eat meat if an easy meal presents itself.

  • Scientific Name: Metynnis argenteus
  • Social Grouping: Groups
  • IUCN Red List: NE – Not Evaluated or not listed


The Silver Dollar is a very deep-bodied fish with a round, almost disklike shape that is very compressed laterally. They can reach almost 6 inches (15 cm) in length and live for 10 years or more in captivity. Their silver color has slight green and blue tints in the right light with some hints of red. The anal fin of the male is edged in red. In some habitats, they will have small dots on their sides.

Metynnis argenteus is very similar to another member of the genus, Metynnis hypsauchen, and both fish are sold in the hobby under the name “Silver Dollar”. The latter species is sometimes referred to as the Plain Metynnis in an effort to distinguish it from its close relation. They are virtually identical in terms of appearance and care requirements. The two species can be told apart as M. hypsauchen has a black blotch located slightly above and behind each eye. In addition to these two species, the Spotted Metynnis M. lippincottianus is also occasionally seen for sale.

  • Size of fish – inches: 5.9 inches (15.01 cm)
  • Lifespan: 10 years – They have a lifespan of 10 years or longer in captivity.

Fish Keeping Difficulty

Silver Dollar Fish are fairly hardy and easy to care for. Although this fish is fairly durable, the aquarist must be prepared to maintain a very large tank. They are suggested for a fish keeper with some experience as a school or 5 or more will require an aquarium of 75 gallons or larger.

  • Aquarium Hardiness: Moderately hardy
  • Aquarist Experience Level: Intermediate

Foods and Feeding

They are omnivores, but are primarily herbivorous in their dietary preference. The Silver Dollar will generally eat mainly vegetable foodstuffs, including a variety of plants, lettuces, cress, chickweed, and large vegetable flakes. A good spirulina formula would be beneficial. These fish will enjoy the occasional treat of bloodworms and brine shrimp. This fish prefers to eat multiple times a day. Offer only what they can consume in 3 minutes or less at each feeding.

  • Diet Type: Herbivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Vegetable Food: All of Diet – Lettuce, Spinach, peas, carrots, cucumbers, fruits, and boiled potatoes make great treats.
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day

Aquarium Care

The Silver Dollar is easy to care for provided their water is kept clean. Aquariums are closed systems, and regardless of size, all need some maintenance. Over time, decomposing organic matter, nitrates, and phosphate build up and water hardness increases due to evaporation. To combat these ever-changing conditions, water should be replaced on a regular basis, especially if the tank is densely stocked. At least 25 to 50% of the tank water should be replaced every other week.

  • Water Changes: Bi-weekly

Aquarium Setup

The Silver Dollar prefers a shallow tank and will occupy parts of the aquarium. This big fish needs a large aquarium with spacious open areas for swimming. A school of 5 or more individuals will require an aquarium of at least 75 gallons. Juveniles can be kept in a smaller 4-foot (122 cm) long, 50 to 55 gallon (190 – 208 L) tank, but they grow quickly when well fed and will soon need a lot more space.

Silver Dollars are hardy and quite disease resistant, so they can handle a variety of water conditions. They need clean water, so good filtration and a moderate water flow are important. A large canister filter will work best for this fish. Add a couple power heads to give the tank great water movement and keep the oxygen level high. With larger Silver Dollars, glass heaters are not recommended. These fish are very active and can easily shatter the heater. Make sure to keep the tank securety covered as fish will jump when startled.

This nervous fish prefers slightly dim lighting and a dark gravel substrate. There needs to be a lot of open space, but the decor also needs to provide hiding places, which can be accomplished with driftwood and solid rock structures. Most plants will be a food source or this vegetable loving fish. Yet, although the Silver Dollar does like to eat plants, hardy varieties that are not so tasty, like java fern and hornwort, may not be bothered. You can also use artificial plastic or silk plants as an alternative.

  • Minimum Tank Size: 75 gal (284 L) – When small they can be kept in a 4-foot long, 50 to 55 gallon aquarium, but they are fast growers and will soon need a larger tank.
  • Suitable for Nano Tank: No
  • Substrate Type: Any
  • Lighting Needs: Low – subdued lighting
  • Temperature: 75.0 to 82.0° F (23.9 to 27.8&deg C)
  • Breeding Temperature: 80.5° F – Breeding temperatures are between 79 and 82° F (26 – 28° C).
  • Range ph: 5.5-7.5 – Breeding ph is between 6.0 and 7.0.
  • Hardness Range: 4 – 18 dGH – For breeding, hardness needs to be below 8 dGH.
  • Brackish: No
  • Water Movement: Moderate
  • Water Region: Middle – These fish will swim in all areas of the aquarium but mainly in the middle.

Social Behaviors

Silver Dollars are large, peaceful, schooling fish. They are great community fish, but are best in groups of 5 or more of their own kind as they can be skittish. If kept singly and without places for retreat, they generally become reclusive.

These fish are great in a large community tank with other large peaceful fish. Smaller community fish will likely be eaten by large Silver Dollars. Good tankmates include the larger peaceful catfish like Loricarids (plecostomus), Doradids (Rafael Catfish), and Pimelodids. They can also be kept with other Silver Dollar species, the more peaceful South and Central American Cichlids, Pacus, Arawana, and Anostomus.

  • Venomous: No
  • Temperament: Peaceful – Although this fish is peaceful, it is best to have similar-sized tankmates.
  • Compatible with:
    • Same species – conspecifics: Yes – They are most comfortable when kept in schools of 5 or more individuals.
    • Peaceful fish (): Safe – They are great companions with large peaceful tankmates, but smaller fish may be eaten.
    • Semi-Aggressive (): Threat
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Monitor
    • Shrimps, Crabs, Snails: Safe – not aggressive
    • Plants: Threat

Sexual differences

The male’s anal fin is longer and tinged with red.

Breeding / Reproduction

Silver Dollar Fish are easy to spawn in captivity. In fact, they will occasionally spawn in the aquarium if they have a large, comfortable environment. In the wild, they spawn in groups in the shallow, heavily vegetated areas of flooded rivers and tributaries. For the best success in finding breeding pairs, start with half a dozen or more juveniles and raise them to maturity. They will reach sexual maturity at about 1 year of age, usually around 4″ in length, though the size is variable.

They are naturally group spawners, but they can also be bred in pairs. Breeding pairs should be removed from their school. To optimize success, it’s best to condition the males and females in separate tanks prior to breeding. For about 7 to 10 days, feed them a high quality plant and vegetable diet. Then select a breeding pair or small group and transfer them into the breeding tank. When ready to spawn, the males will darken, especially around the anal, caudal and dorsal fins, and their hints of red will intensify.

A separate, shallow breeding tank with soft, warm water is best for a successful spawn and will help to get the best number of fry. The breeding tank should be at least 40 gallons for a pair, but a group will need larger aquarium. The water should be soft and slightly acidic, with a pH 6.0-7.0 and a hardness of 4-8° dGH. A temperature of around 79 to 82° F (26 – 29° C) is recommended, though some have reported successful spawns in temperatures up to 90 ° F (32° C). A small, air-powered sponge filter is needed for filtration and to provide a gentle water flow.

Keep the breeding tank slightly dim and provide clumps of spawning mops or java moss for the eggs to fall on. Also, provide clumps of floating plants on the surface for the breeders to spawn between. To stimulate a spawn, the males will court the females by chasing them around the tank and shimmy up next to them. When a female is ready to breed, she will release her eggs near or in the floating plants, and the male will fertilize them. The eggs are not adhesive and will fall to the bottom of the tank. Each female can produce up to 2000 eggs, which are transparent and slightly yellow.

The parents generally don’t eat the eggs, so there is no need to remove them, but it is easier to raise the fry if the parents are removed. The eggs will hatch in about 3 days, and the fry will be free-swimming 6 to 9 days later. For the first few days, feed the fry infusoria-type foods until they can feed on small plankton, brine shrimp nauplii, powdered foods, and vegetable flake. The fry are fast growing when well fed and will reach adult size in 6 to 8 months. See Breeding Freshwater Fish: Characins for a general description of breeding processes, and see Fish Food for Fry for information about types of foods for raising the young.

  • Ease of Breeding: Easy – Breeding is not difficult, but it is only possible in a very large tank with precise water conditions.

Fish Diseases

The Silver Dollar is very hardy, and disease is not usually a problem in a well-maintained aquarium. That being said, there is no guarantee that you won’t have to deal with health problems or disease. Anything you add to your tank can introduce disease. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so as not to upset the balance.

A good thing about the Silver Dollar is that due to their resilience, an outbreak of disease can often be limited to just one or a few fishes if dealt with at an early stage. When keeping more sensitive types of fish, it is common for all fishes to be infected even before the first warning signs can be noticed. The best way to proactively prevent disease is to give your Silver Dollar the proper environment and a well-balanced diet. The more closely their environment resembles their natural habitat, the less stress the fish will have, making them healthier and happier. Stressed fish are more likely to acquire disease.

As with most fish, they are prone to skin flukes, parasitic infestations (protozoa, worms, etc.), ichthyobodo infection, parasitic infestations (protozoa, worms, etc.), bacterial infections (general), and bacterial disease. Aquarists should read up on common tank diseases. Knowing the signs and catching and treating them early makes a huge difference. For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.


The Silver Dollar Fish is readily available in pet stores and online and is reasonably priced.



 Silver dollar – Metynnis argenteus (Image Credit: Greg Hume, Wikimedia Commons CC BY-SA 4.0 International)