What to Know About Goldfish

Medically Reviewed by Vanesa Farmer, DVM on November 29, 2022
4 min read

Goldfish are a common fish found in the wild, in pet stores, and in households worldwide. 

Since the 1600s, when these fish were initially introduced to the United States, they have become widespread throughout the U.S. but are not considered invasive in the wild, despite large populations. In fact, despite their existence in the wild, they usually remain below problematic proportions. Goldfish come in many varieties and have various uses. Besides being a popular pet choice, goldfish are also used as feeder fish, bait, and to be kept in backyard ponds for their natural beauty. These uses contribute to the whopping 480 million goldfish sold annually.

Before you purchase a goldfish, it’s important to understand its physical and behavioral characteristics. 

Physical Characteristics 

Despite their name implying otherwise, goldfish come in various colors and sizes. Common colors include gold, red, orange, white, and olive green. Most goldfish have large eyes and lack scales on their head. They also usually have no barbels on the upper jaws. In terms of goldfish size, they usually grow to be around 5-8 inches in length, but some can grow up to almost 2 feet long and can weigh up to 6 pounds.

Behavioral Characteristics

Goldfish are social creatures who form schools in the wild, which helps them protect themselves against predators. These fish are often most active during dusk and dawn. 

Since goldfish are social fish, they should be kept in pairs of two or more. Due to their social behaviors and intelligence, they often interact with each other and their human owners.

One behavior you might notice from your pet goldfish is that they tend to search for food at the bottom of their tanks, typically by digging around. They will sometimes confuse gravel for food and try to consume it, only to spit it back out once they’ve realized it’s not food.

When deciding to keep goldfish, it’s good to learn what caring for a goldfish entails so that you provide them with an appropriate habitat and diet to keep them comfortable and healthy.

Goldfish Habitat

Goldfish can grow to be quite big, with some reaching 12 inches in length. Because of their potential size, be careful to provide your goldfish with adequate space. An aquarium for one goldfish should be around 25-30 gallons.

Most fish require plants in their aquariums. Goldfish are no different. Some common types of plants to include in a goldfish’s habitat include: 

  • African Water Fern
  • Anacharis
  • Dwarf Anubias
  • Frogbit
  • Hornwort
  • Java Fern
  • Java Moss
  • Parrot Feather
  • Water Sprite

When choosing what aquatic plants to include in your goldfish’s aquarium, you’ll want to consider the aquarium’s temperature and lighting. Both the plants and goldfish need to be able to thrive at the same temperature. Since goldfish do well in temperatures around 70 Fahrenheit, choose aquatic plants that also can live in 70 Fahrenheit water. Choosing plants that require a significantly different temperature, whether colder or warmer, will increase the likelihood of the plants dying and rotting. Additionally, if your aquarium has more or less lighting, you’ll want to ensure your plant selection can do well in those lighting situations.

Besides plants, you’ll want to add plenty of substrates, decorations, and shelter options. You can also add equipment such as heaters, UV sterilizers, lights, filters, and automatic feeders.

Goldfish Diet

Goldfish are opportunistic feeders and will eat as much food as you give them. You mustn’t overfeed them as this can lead to complications such as constipation which can have deadly consequences. Symptoms of an overfed goldfish include lethargy and a bloated abdomen. If you notice these symptoms, you’ll want to cut back on how much you feed your goldfish.

Goldfish will eat whatever they encounter in the wild, including algae, aquatic plants, insects, and tadpoles. They’ll even eat other fish. 

Pet goldfish can be fed a variety of items, too, including fish pellets, fish flakes, freeze-dried and frozen foods such as brine shrimp and water fleas, vegetables and fruits, and live food such as certain types of worms and aquarium snails. 

How much and how often you feed your goldfish will depend on certain factors, including the age and size of your goldfish and the temperature of the water. Goldfish that are younger than one year have a faster metabolism and should be fed two to three times a day. As they age, their metabolism slows, so goldfish that are older than a year should be fed once a day. The water’s temperature can also contribute to a slower or faster metabolism. Adult goldfish kept in the usual 65-70 Fahrenheit can be kept on a normal diet of being fed once a day. Goldfish in colder conditions, such as outside ponds, should be fed a diet to match their slowed metabolism. Avoid feeding too much protein to goldfish kept in colder water.

Never feed your goldfish bread, fish food blocks, or mammalian proteins.

Goldfish are resilient creatures and can withstand several poor living conditions. However, goldfish still require proper care to live happy and healthy lifestyles. Failure to give your goldfish adequate care can increase the likelihood of it contracting diseases, falling ill, or even dying.

Goldfish can become sick if not properly cared for. Overfeeding your goldfish can contribute to constipation, leading to goldfish swim bladder disease, which causes your fish to swim sideways or upside down. Goldfish are often common hosts for parasites. When introducing a new goldfish to your home, you’ll want to quarantine it for a while to ensure that no parasites are present. In addition to parasites, goldfish are also susceptible to bacterial and fungal infections.

Also, it’s important to keep uneaten food scooped out from your goldfish’s aquarium. Uneaten food can lead to high traces of ammonia, which can cause your goldfish to become ill. 

The average goldfish lifespan is around 5-10 years. However, some goldfish can live up to 30 years old. How long your goldfish lives will depend on how well it’s taken care of.