Goldfish are a hardy aquatic species. They can deal with temperature fluctuations, changes in pH, cloudy water, and even low dissolved oxygen levels.
If released into the wild, goldfish can group up into what’s called a school. But they don’t need companions to be happy in captivity and are fine if kept separately in a tank.
Because they’re not an aggressive species, they can be paired in a tank with fish that aren’t vastly different in size. They’re also smarter than may meet the eye. Researchers found that they can be trained to tell the difference between Bach and Stravinsky’s classical music.
In captivity, goldfish usually eat pellet or flake food. Supplements, however, are recommended to better mimic their natural diet. In nature, they eat worms, larvae, small crustaceans like brine shrimp, and even salad fixings like peas and lettuce. It’s recommended that goldfish owners add greenery to the bowl since the fish like eating live plants.