dollar

Silver dollar is a common name given to a number of species of Metynnis, a tropical fish belonging to the Characidae family which is closely related to piranha and pacu. Originating in the Tapajós River basin in South America, this somewhat round-shaped silver fish with slight red-tinged anal fin is mostly found in tanks kept by fish-keeping hobbyists. It will grow to a maximum length of 14 centimeters (5.5 inches).
The silver dollar is a peaceful schooling species that spends most of its time in the mid- to upper-level of the water. Its maximum lifespan is more than 10 years. A chin-layer, the adult fish will spawn around 2,000 eggs. This breeding occurs in soft, warm water in low light.

Silver dollars natively live in a tropical climate in the sides of weedy rivers. They prefer water with a pH of 5–7, a water hardness of up to 15 dGH, and an ideal temperature range of 24–28 °C (75–82 °F). Their diet is almost exclusively vegetarian and in captivity they will often eat all the plants in a tank. They will also eat worms and small insects.
The silver dollar is listed as semi-aggressive but it is very mellow like the pacu. These fish can be kept in community tanks with fish that can't fit in their mouths, so don't put a full-grown silver dollar with neon tetras and guppies. These fish can also be kept with larger fish like oscars, pikes, and larger catfish when full grown.