How Long Do Goldfish Live and How Big Do They Get?

Looking after a pet can teach your child about compassion, responsibility and coping with loss. For their first animal companion, though, it makes sense to choose something small and relatively low maintenance.

One family favorite that fits the bill perfectly is the goldfish. Before you head to the pet store, read on for the basics about the Carassius auratus—from life expectancy to food advice.

How Long Can Goldfish Live?

School of goldfish swimming a pond
School of goldfish in a pond. Fish in pet stores are sometimes kept in overcrowded tanks and a stressed fish is at greater risk of succumbing to disease. George Melin/Getty Images

Adam Jones, editor of The Goldfish Tank website, suggests this mainstay of indoor aquariums can have a surprisingly long life—if cared for correctly.

"Typically goldfish have a lifespan of about 10 to 15 years," he told Newsweek. "Some varieties can even live up to 30 years old.

"Unfortunately, most goldfish do not live this long due to improper care and inadequate housing conditions. Proper housing facilities are a necessity to meet both behavioral and physiological needs."

Jones recommends caution when shopping for your pet goldfish, because poor living conditions in early life can shorten their lifespan.

"You want to ensure that the breeder isn't keeping them in an overpopulated or undersized tank.

"Healthy fish should have clear and bright coloration on their bodies and they will swim around the tank without any undue effort.

"A tank too small can stunt the growth of your goldfish, cause them to bob to the surface, and may even lead to a premature death."

How Big Do Goldfish Get?

Aquarium native hardy gold fish, Red Fantail
A Fantail goldfish. Goldfish can grow to 10 inches or more in ponds, but are unlikely to reach that length if they are kept in an aquarium. EuToch/Getty Images

The size of a goldfish is "dependent on the care and treatment of the fish," as well as "the breed and genetics," according to Jones.

He added: "Goldfish kept as pets contained in indoor smaller tanks usually grow to about 1 to 2 inches in length, and never really surpass 6 inches. However, in ponds, they can grow well over 10 inches.

"For optimal growth, your goldfish needs around 29 percent protein and 12 percent fat in their diet. Provided you follow this, your goldfish should grow to 2 inches over a course of six months and to 3 inches by the end of its first year."

The biggest goldfish ever recorded belonged to a man in the Netherlands and was measured at 18.7 inches long in 2003.

Goldfish that are more than 1 foot long are not all that unusual. In July 2021, officials in Minnesota urged pet owners to stop disposing of unwanted goldfish in lakes or ponds.

They highlighted the problem by sharing images of goldfish that had grown to enormous size after their release, damaging water quality and plant life in lakes.

What Do Goldfish Eat?

Goldfish swimming in a tank
Goldfish swimming in a tank. It's easier to stop your fish overfeeding if it's not in a pond. MirekKijewski/Getty Images

Goldfish eat a variety of insects, plants and crustaceans. For pets, Jones recommends a mix of flakes, pellets, live food and vegetables.

They are also "opportunistic feeders," he said, and will continue to eat "even if it is to their detriment."

He added: "By keeping a goldfish in a tank, rather than a pond, you will be able to monitor their diet and ensure they don't overeat as you will control their feeding.

"Whilst you still have to feed goldfish which live in ponds, they are open to the environment around them. This means they will feed on insects which fall onto the pond water, as well as algae too."

How to Care for a Goldfish

Goldfish in aquarium with green plants, snag
Goldfish in aquarium. Keep a close eye on your pets for any changes in appearance or behavior. This will help owners to address concerns before they become major health problems. sergio_kumer/Getty Images

Before you buy a goldfish, consider the size of tank—not bowl—you will need to place somewhere in your home.

"Each fish should have a minimum of 6 gallons of water to itself, and the tank should ideally be no smaller than 10 gallons. So, the more fish you have, the larger the tank will need to be," said Jones.

Your tank will also need:

  • A thermometer to ensure the water remains at the correct temperature
  • An aquarium filter to prevent water from becoming toxic
  • Sufficient hiding places to maintain your fish's natural instincts

The tank needs to be cleaned regularly. "This simply requires you to change about 10 to 15 percent of the water, and refill with de-chlorinated water," said Jones, who offers more guidance for new goldfish parents online.

Goldfish goldfish single one in aquarium
Your goldfish tank should contain at least 10 gallons of water. Each fish you add should get their "own" 6 gallons or more. Altinosmanaj/Getty Images