Goldfish are hardy and one of the more popular fish that hobbyists keep, regardless of experience. Because of their bright colors and wide variety, they are attractive fish for all ages.
Goldfish Grow Large
There are different species and types of goldfish, and most make good aquarium pets. But your average goldfish can grow to be 6 to 8 inches long, some reaching upward to 12 inches long. Small, 1-inch comets can grow to be 12-inch adults, whereas adult bubble eye goldfish may only grow to be 8 inches.
Use at Least Ten Gallons
A 10-gallon aquarium will be a fine starter size tank for two to four small goldfish, but the goldfish will not reach their proper adult size unless they are placed in a larger aquarium. The rule of thumb is 1 gallon of water per inch of fish. Some fish hobbyists believe you should have a 20-gallon tank for one fancy goldfish, and 10 gallons per each one you add to the aquarium.