The Silver Dollar Fish Metynnis argenteus looks just as its name implies, round and 'covered with silver. These fish are characins called "Silver Dollar" because their body shape is almost round and is very compressed laterally. Their scientific name says it all, with the genus term Metynnis meaning "with plowshare" and the species name argenteus meaning "covered with silver".
The M. argenteus characins are generally a silver color, but with slight green and blue tints in the right light. There are also hints of red, 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, also known as the Silver Dollar, are virtually identical in both looks and aquarium care. Both these species are commonly available to the aquarist. They can be only be distinguished by a black blotch or shoulder patch found slightly above and behind each eye on the M. hypsauchen.
There are a number of fish known by the common name Silver Dollar. Most of them are members of the Metynnis genus which contains 14 described species and the Myloplus genus with only 2 described species. However M. argenteus along with 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, and others like 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 so on.
The peaceful Silver Dollar is a choice fish for many aquarists who want a community aquarium with good sized inhabitants. The Silver Dollar, though very peaceful, gets rather large and needs a good sized aquarium. They are a lively fish and like to hang out in schools, so get several if you can.
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 plastic plants.
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. There information about their occurrences vary. Atlas references say they are found in Guyana, the Amazon east of Rio Negro, to Paraguay. This may actually be the occurrence of its close relative Metynnis hypsauchen, also known as the Silver Dollar Fish, as other sources suggest M. argenteus is possibly endemic to the Tapajós River basin in Brazil. This species is a schooling fish, mostly inhabiting heavily grown smaller tributaries and feeding primarily on vegetable matter. In nature they are normally a herbivore 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 disk like shape that is very compressed laterally. They can get reach almost 6 inches (15 cm) in length and can live for 10 years or more in captivity. They are a silver color with slight green and blue tints in the right light. There are also hints of red, especially the anal fin of the male which is edged in red. In some habitats they will have small dots on their sides.
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 4 or more will require an aquarium of 75 gallons or larger.
Aquarium Hardiness: Moderately hardy
Aquarist Experience Level: Intermediate
Foods and Feeding
Since they are herbivorous the Silver Dollar will generally eat mainly vegetable foodstuffs including a variety of plants, lettuce, cress, chickweed, and large vegetable flake. A good spirulina formula would be beneficial. These fish like to get the occasional treat of bloodworms and brine shrimp. This tetra prefers to eat multiple times a day. Offer only what they can consume in 3 minutes or less with multiple feedings per day.
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
The Silver Dollar is easy to care for provided the water is kept clean. Aquariums are closed systems and regardless on size all need some maintenance. Over time decomposing organic matter, nitrates, and phosphate build up and the 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 - 50% of the tank water should be replaced every other week.
Water Changes: Bi-weekly
The Silver Dollar is a large fish that will occupy all parts of the aquarium and need spacious open areas for swimming. To keep a school or 4 individuals or more will require an aquarium of at least 75 gallons. Juveniles can be kept in a smaller tank, but they grow quickly when well fed and will soon need a much larger tank.
They are hardy and quite disease resistant, so can handle a variety of water conditions. They need clean water, so good filtration is important and a moderate water flow. A large canister filter will work best for this fish. Adding a couple power heads will give the tank great water movement and keep the oxygen level high. With larger Silver Dollars a glass heaters are not recommended. These fish are very active and can easily shatter the heater. Make sure to have a secure lid because these fish are jumpers when startled.
Minimum Tank Size: 75 gal (284 L)
Suitable for Nano Tank: No
Substrate Type: Any
Lighting Needs: Moderate - normal lighting
Temperature: 75.0 to 82.0° F (23.9 to 27.8° C)
Breeding Temperature: 80.5° F - Breeding temperatures are between 79 - 82° F (26 - 28° C).
Range ph: 5.5-7.5 - Breeding ph is between 6.0 - 7.0.
Hardness Range: 4 - 18 dGH - For breeding, hardness needs to be below 10° dGH.
Water Movement: Moderate
Water Region: Middle - These fish will swim all over but mainly in the middle of the aquarium.
The Silver Dollar is a peaceful fish and great in a large community tank with other large peaceful fish. Smaller community fish won't fare as well, as they will likely be eaten by large Silver Dollars. These fish are best in groups of 4 or more. Good tankmates include the larger peaceful catfish like plecostomus and the doradids.
Temperament: Peaceful - Although this fish is peaceful it is best to have similar sized tankmates.
Same species - conspecifics: Yes - They are most comfortable when kept in schools of 4 or more individuals.
Peaceful fish (): Safe
Semi-Aggressive (): Threat
Aggressive (): Threat
Large Semi-Aggressive (): Threat
Large Aggressive, Predatory (): Threat
Slow Swimmers & Eaters (): Monitor
Shrimps, Crabs, Snails: Safe - not aggressive
Sex: Sexual differences
The male has a longer anal fin which has a red tinge on the front of it.
Breeding / Reproduction
The Silver Dollar Fish are easy to spawn, they will do so in a school. Suggested water conditions: 79-82° F (26-28° C); pH 6.0-7.0; below 10° dGH. Place clumps of plants on the surface so they will spawn in between them. The female will lay up to 2000 eggs which will fall to the bottom and hatch after 3 days. The parents will not eat the eggs so there is no need to remove them. The fry will attach themselves to a surface and eat small plankton. See the general description of how to breed characin fish, see Breeding Freshwater Fish: Characins.
Ease of Breeding: Difficult - Breeding is not difficult, but it is only possible in a very large tank with precise water conditions.
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 bring disease to your tank. 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 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 you deal with it 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 Flame Tetra the proper environment and give them a well balanced diet. The closer to their natural habitat the less stress the fish will have, making them healthier and happy. 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. It is recommended to read up on the 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.
Zebo - 2015-02-08 I have 3 Silver dollars...they are full grown as I have had them for almost 7 years. One of them is huge and the other two are only about 4 inches long. I assume they are different varieties as they have never gotten bigger. I lost one of them when he ate the plastic plants and died from it, so I recommend no fake plants. If you feed them a supplement of algae tabs and romaine you can also put live plants in the tank. They will nibble on them, but that's what they do...you just have to buy more plants once in a while.
Ray - 2014-10-04 I have a female silver dollar purchased September 1990. It is now 24 years old. The only documentation I have is family members who have seen it over the years. My wife and I are amazed that it is still alive and wonder how much longer it will live!
Clarice Brough - 2014-10-09 Wow! That is awesome. They average 10 years or more, but you'll have to let us know what the 'or more' means, because you're breaking new ground:)
Theresa - 2015-01-15 My mother inherited my two silver dollars which I originally purchased while living at home back in 1994 making them about 21 years old. They stayed after I moved out. They are still as energetic as ever--the only noticeable differnce is that they do have cataracts. She used to call them her 'teenagers', but I guess they have outgrown that phase.