There are a lot of common names to describe and sell tropical fish. Some work, and some do not. Does a tire track eel’s body really resemble tire tracks? What is so angelic-looking about an angelfish? However, in the case of Metynnis hypsauchen, the moniker of “silver dollar” is not so erroneous a descriptor.
There are other species of fish in the Metynnis family with similar comportment and coloration, and many are commonly referred to as “silver dollars,” as well. In this article, we will be discussing the most commonly seen, the true silver dollar: Metynnis hypsauchen. Let it be known, however, that its cousins have similar requirements, and with a little extra research, they can also be kept as aquarium fish.
The silver dollar is a common fish in the aquarium hobby and has been since I started keeping fish more than 37 years ago. It has maintained its popularity through the years due to its sharp looks, ease of keeping, disposition, hardiness and relative low cost. Granted, it does not possess the garish coloring often associated with some livebearers, tetras and discus, but its shape, silvery body sheen and distinctive red anal fin capture the eye.
Beginners are often intrigued by the silver dollar. Generally they can do well in a beginner’s small tank — but not for long. Being members of the characoid (tetra) family, they are an Amazonian schooling fish. While schooling fish can be kept alone (as silver dollars often are), they thrive in the presence of conspecifics and will even show off an accentuated coloration in this atmosphere.
Silver Dollar Behavior
As far as tank behavior, silver dollars are peaceful residents. While they may be larger than their tankmates, they rarely show belligerent behavior toward others. Always be careful, however, when placing fish like tiny neon tetras with them. There is a fishkeeper’s adage: “If it fits in the mouth, it will find its way into the mouth.” For the most part, silver dollars go nicely with livebearers, barbs, tetras and other tropical fish of that size. Generally speaking, you do not need to worry about the silver dollar’s tankmates.
Silver dollars are primarily vegetarian in nature. This does not mean that they will turn down brine shrimp, live worms and other meaty offerings. Rather, given their choice of menu items, they would prefer to munch on your beautifully arranged aquarium plants. Some aquarists shudder at the thought of using the plastic variety of flora, however you can be certain that the Amazon swords you are so fond of will quickly become a snack for your silver dollars. You’ll need to choose one over the other. Keep in mind, for your silver dollars to stay in mint condition, they will need a significant vegetable-based diet.
Unless your tank is overgrown with algae, don’t expect that your silver dollars will get their nutritive requirements by scraping the glass, á la pleco cats. These fish eagerly devour commercially packaged vegetable-based flake foods. Spirulina is one form of algae-based flake food that is primarily vegetable matter in content. Don’t be shy about offering greens from your kitchen, either. Stay away from iceberg lettuce, though, as there is no nutritional value to it. You can offer any other leafy green vegetable that you might put in a salad. Help the fish out by softening the greens in advance by partially boiling the items before feeding.
I would wager to say that most hobbyists at one time or another have had some silver dollars in their aquariums. I would also venture to say that no one gave up on these fish because of the difficulty in keeping them, feeding them or for lack of activity. Hobbyists have found that silver dollars are more prone to outbreaks of ich than other fish. The other factor that makes an aquarist (especially beginners) shy away from these fish is learning that they can grow large. Let’s look at both of these factors and see if we can conquer these apprehensions with some good logical advice.
First, let’s deal with ich. Being Amazonian fish, the natural water preference would be soft, with a pH value in the range of 6.5 to 6.8. Like many other freshwater fish, their ability to acclimatize to varying water conditions is commendable. They are primarily imported after being wild-caught, so just making it through the trauma of trans-continental shipping is credence to their adaptability.
However, if pushed too far, their immune systems will break down. An example of this facet would be placing them in hard water immediately after purchase with a pH value in the 8.0 or higher range. It’s a good idea to know the pH of the store water you purchase your fish from to compare it to yours. If the difference is more than one point, I suggest gradually raising the tank temperature to 80 degrees Fahrenheit for approximately one week. Subsequently, slowly lower it back to the mid 70s range where they thrive. This process should greatly reduce any possible outbreaks of ich. Commercially available stress reducers are recommended during this process, as well.
Silver Dollar Size
Let’s deal with silver dollars’ growth potential. They can grow fairly large. It’s funny how people derive their notions of certain animals. Many a friend will peer into my 120-gallon tank and gasp unknowingly at a silver dollar and ask, “Is that a piranha?” First, I tell them to put their hand in and find out. Then I tell them that piranhas generally do not get that large. Actually, the piranha and the silver dollar are cousins in the characoid family.
It is not unusual to see most silver dollars (Metynnis) for sale in a quarter-size range. Their name, however, is derived not only from their silvery appearance; many are also sold in a size range equal to that of a true silver dollar coin (Eisenhower variety). Regardless of purchase size, these schooling fish should be kept in shoals of no less than three. Hence, it won’t be too long before they outgrow a 10- or 20-gallon aquarium. I would refer to them as “tankbusters,” a name reserved for the likes of tinfoil barbs and other species that will outgrow even a 55-gallon tank in not too much time. I have had several Metynnis that have gone from a quarter size to 5-inches-plus size in a year and a half.
Living in aquariums too small for their roaming pleasure will stress them. When they are uncomfortable, they become quite skittish. The slightest touch to the tank or your sudden appearance will send them careening off of the sides of your aquarium. A tank in the 30-gallon range will house three full-grown silver dollars nicely. Keep it well planted with artificial plants, smooth rocks or driftwood. They will destroy most live plants you might have considered.
The species I mentioned here, Metynnis hypsauchen, is not the only fish sold as a “silver dollar.” It is, however, one of the most popular of silver disc-shaped fish labeled with this moniker; you may encounter Metynnis argenteus or M. luna. Regardless of the species, you are most likely to find that the behavioral characteristics I have highlighted here will hold true to most of these fish. As with any new species of aquarium fish you keep, it always pays to do your research ahead of time.