Silver Dollar

About

Silver dollar (Metynnis hypsauchen) is one of those fish that causes a double-take at the fish store. That flat, disc-shaped, gleaming silver body really does look like it belongs in piranha territory, and for good reason. This species is a close relative of piranhas and shares that impressive dentition, though it uses its teeth primarily for plant material rather than flesh. It hails from the Amazon and Paraguay river basins as well as rivers draining the northern Guiana Shield, where it typically schools in open water. In the aquarium it stays peaceful with similarly-sized companions and tends to cruise the middle and upper water column, which means bottom-dwelling tankmates like larger plecos or doradid catfish make natural partners. The key word there is "larger". Genuinely small fish are at risk of being eaten. A group of at least five is the way to go, since these are social animals that do better with company. Worth knowing: this species is frequently sold alongside the very similar Metynnis argenteus under the same "silver dollar" label. The easiest way to tell them apart is a small dark blotch just behind and above each eye on this species. A striped color form also appears in the hobby now and then. Generally a forgiving fish for newer keepers willing to provide adequate space.