Goldfish: Care, Diet, Breeding, Facts, & More

The common goldfish (Carassius auratus) is one of the oldest domesticated fish in the world. These beautiful fish have been line bred to create a diverse range of different breeds for the aquarium hobby. These fish are now looking completely different from the original wild type of goldfish.

These fish are one of the most common fish in the aquarium hobby and countless articles have been written about them. However, these fish still get mistreated and not many people seem to care for them the proper way.

So we made this guide to help you understand this fish fully and provide it the right care it needs. We will cover all the aspects of its care to make you ready for owning a goldfish. 

Species Profile & Overview

Goldfish were first domesticated in ancient China hundreds of years ago. Goldfish is a type of crucian carp that has been selectively bred over many hundreds of years to develop beautiful red coloration and body shapes. Both domesticated goldfish and their wild-type ancestor are technically the same fish but after years of line breeding, there are slight differences in their genetics now.

Goldfish is typically a pond fish and has been kept in ponds from the beginning of its domestication. With the boom of the aquarium hobby in the past few centuries this fish is now bred to create smaller variations that are able to live in smaller spaces like aquariums.

In the wild, Goldfish can live in rivers, streams, lakes, ponds, or any other body of water. This makes them super hardy fish that can easily spread and destroy the habitat of native species in any region of the world. This is why you should never release your goldfish in lakes or rivers. 

Appearance & Types

A Group Of Common Goldfish In Aquarium
Common Goldfish

The wild crucian carp is a dull silvery-brown colored fish that has a similar body shape to a common goldfish. However, the famous goldfish is line-bred over hundreds of years to develop deep orange and yellow color pigments. 

This beautiful aquarium fish has now bred to many different shapes that look very different from the common goldfish or its wild type the crucian carp. These fancy versions of the common goldfish are being graded and sold by their unique appearance and colorations. 

Nowadays there are many fancier types of this fish available in the market. The most famous types of goldfish are Fantail, Oranda, Ryukin, Veiltail, and BubbleEye. These fish are smaller than the common goldfish and are more sought after by fishkeepers. 

Goldfish are the smaller cousins of Koi Fish. They both are a type of carp fish that have been domesticated by humans for their meat and appearance. The main differences between koi and goldfish are their size, body shape, and the fact that goldfish lack barbels or whiskers on the sides of their mouth. 

Goldfish are sexual dimorphism species that males and females have visible differences. If you are not an expert fish keeper, sometimes it can be hard to identify the gender of this fish. The most obvious way of identifying a male from a female is by looking at the anal fin of the fish. Males have long and pointed anal fins whereas females have curved and short anal fins. 

Females are often larger than males and develop a rounder and thicker belly area. This can be more visible during the breeding season as females will get full of eggs.

Adult Size

Goldfish are large species that grow to about 7 – 16 inches in length. The common goldfish can easily reach 16 inches when enough space and food are available. The fancier species, however, tend to stay smaller and around 7 inches when fully grown.

This is why you should never keep a goldfish in a fishbowl. These large species need enough space to naturally grow and experience a healthy life. Keeping a large fish of this size in a tiny fish bowl is unhealthy and super harmful to the fish.

Lifespan

Under the right conditions, goldfish can live over 20 years in captivity. However, this fish often experiences a shorter lifespan when kept by new fish keepers. This is because the quality of water and the space they live in is not ideal for a goldfish. 

Behavior and Temperament

Goldfish are generally peaceful species and can get along well with most peaceful, similarly-sized species. However, they are extremely food-motivated species and will eat any small species they can catch or any live plants they can bite. 

These fish are very social species and will come to you for food. You can even hand-feed them! After some time, they will start to recognize their owner and will come to say hi every time you walk by their tank. 

These fish also prefer to live in groups, even though they don’t school together. When you keep multiple goldfish together you might see minor schooling behaviors but that is only them being socializing. 

Goldfish Care

Goldfish are easy to take care of. However, you will need to provide them, at least, with the minimum care requirements they need. With the right diet, tank size, and water conditions, almost anyone can keep these fascinating fish happy and healthy.

In this section, we will walk through all the information you’ll need to a better living environment for your goldfish.

Tank Size

Goldfish needs a 30 gallon tank or larger. While most claim these fish can live in smaller tank sizes we, however, find it to be false. Goldfish, regarding their type, need a tank that is at least 30 gallons to be able to have a healthy life. 

These fish will grow large and need enough space to grow naturally. At the same time, they also produce a lot of waste which almost makes it very hard to keep the water clean in a smaller tank. A large tank can easily handle the bioload of this fish while also giving them enough space to explore. 

We however always recommend getting a bigger tank of 50 gallons or more. These living beauties have long been kept in poor conditions and in small fish bowls that are super unhealthy. Giving them a large tank will extend their lifespan and they can grow naturally without any deformity. 

What To Put In A Goldfish Tank

Common goldfish can live in any tank with almost any decorations except live plants. These vigorous eaters will eat and unroot almost any plant that you place in a tank. However, there are a few plants that seem to do fine in a goldfish aquarium. 

Plants like Cryptocoryne, Buce Plants, Java fern, and Anubias can be placed in a goldfish tank as long as they are secured properly. These plants have hard leaves that goldfish seem to show no interest in eating them. But they will try to uproot them so you will need to attach them securely to objects and decorations. 

You might want to read our detailed guide on types of plant you can keep with Goldfish.

Speaking of decorations, goldfish should have enough space to be able to swim freely. So try to add minimum decorations that can block their way. No sharp or rough objects should be placed in a goldfish tank as they can injure the fish and cause infections or permanent deformities on the fish.

Most fish keepers keep their goldfish in bare-bottom tanks. While this is the best way to minimize damage to the fish, it might not be the most beautiful approach. So we recommend having sand or smaller pebbles in their tanks. Goldfish like to shift the substrate to find food, so smaller substrates like sand will give your fish a natural playground to explore.

Oranda Goldfish In Aquarium
Oranda GoldFish (Fancy Goldfish)

Water Parameters

Goldfish are cold-water aquarium fish and do much better in cooler temperatures. The room temperature is often the best range for these fish but they can also live in cooler or warmer waters. 

Goldfish prefer to be in slow to moderate-moving waters. This is especially true for the fancier varieties that have rounder body shapes. The water should have stable parameters at all times. Sudden changes in water parameters can be harmful to these fish.

Lower amounts of salt will help your goldfish to stay healthier and stay disease free. Most recommend adding a tablespoon of aquarium or sea salt for every 5 gallons of water that your tank can hold. Depending on the water conditions and health of your fish you might slightly increase or decrease this amount.

Below are the ideal tank parameters you can keep goldfish in: 

  • Temperature: 68 – 74 Degrees Fahrenheit 
  • PH: 6.5 – 7.5
  • TDS: 50 – 150 PPM

Lighting

Goldfish are not picky when it comes to the lighting of their tank. They will happily accept all-natural sunlight or a strong aquarium light. These fish are naturally adapted to live in almost any conditions in the wild. They can be found in well-lit shallow areas of ponds or streams around the world. 

A planted LED aquarium light is an ideal light for these fish. Planted LED aquarium lights are usually full-spectrum and have blue lights built in. A blue light will bring out the true red and white coloration of goldfish and make them look much more beautiful.

Filter System

Goldfish produce a lot of waste and they need a strong filtration system to ensure clean water at all times. A proper clean aquarium is essential to the health and well-being of this fish. You might ask then why a goldfish can live in a bowl with no filtration? The answer is easy, keeping this fish in an unhealthy and unfiltered aquarium will drastically lower its lifespan. This is why not many goldfish survive past a few days in a fishbowl.

A strong filter, that can keep up with the bioload produced in a tank, is an absolute necessity for the health of your pet fish. The aquarium filter is the heart of your system and if it fails the whole ecosystem in your tank will collapse.

For optimum health, you should also perform regular water changes. Changing 10% of the water weekly is the best approach to keeping goldfish healthy and happy. 

Common Goldfish Diseases & Health Issues

Goldfish are generally healthy and hardy fish that do not easily get sick if kept in clean conditions. That said, many of the illnesses and infections that these fish experience are due to a lack of proper care from their owners. 

When water parameters are poor or when they do not receive a nutritious diet they can easily get sick. In an aquarium that is regularly cleaned and has stable water parameters, these fish do not appear to contract any illnesses. 

Ich, fin rot, Swim bladder disorder, and Fungal infections like Cotton mouth are among the most common diseases a goldfish can contract. These diseases can get introduced to your tank by adding a new sick fish or naturally develop because of poor water quality.

The best way to prevent illnesses in your tank is to stay on top of your water changes and never overfeed your fish. A good filter will also help to prevent ammonia-related diseases. If your fish got any of these illnesses, you will need to seek professional vet advice on how to cure it the proper way.

Diet and Feeding Requirements

Goldfish are omnivore species and will eat any food they find. In the wild, they feed mainly on insects, plant matter, and crustaceans. You will need to provide them with a similar diet in captivity as well. 

The best way to feed them is to have a few different types of fish food in hand and feed them a mix of all. Because of the popularity of this fish, many dry food products are specifically designed for goldfish. These foods are usually the best foods you can purchase but they still can’t give your fish all the nutrients it needs. 

Because these fish are omnivores, you can feed them fresh vegetables as a fresh source of vitamins and minerals. These fish will happily accept green peas, cucumber, spinach, and other fish-safe vegetables.

Make sure to feed your Goldfish sinking foods as they are bottom-feeding species. Floating foods will force the fish to come to the surface and may gulp air when feeding. This can cause swim bladder disorder in your fish in the long run. 

These fish will constantly eat and simply don’t know how to stop. This means you will have to make sure not to feed them too much. Simply add enough food that they can finish within 2 – 3 minutes. Feeding more than this can cause ammonia spikes and trigger diseases in your fish.  

Breeding Goldfish

Goldfish are egg scatterers and they can breed in a home aquarium. The breeding process can become violent if you have more males than trying to mate with a female. So if you see any aggressive behavior during the breeding season you may want to separate the fish. 

If you see your fish successfully laid their eggs and you want the eggs to hatch, then you should separate the eggs from the adult fish. Adult fish will eat all the eggs if you do not separate them.

Goldfish can lay up to 1000 eggs in a single spawn. Eggs are sticky and will attach to any available surface. If you have live plants, these fish will try to lay their eggs on live plants. Depending on the water temperature and hardness, the eggs will hatch within 48 to 72 hours. 

Tank Mates

When it comes to picking tankmates for this fish, it is best to keep them with other goldfish or koi. This makes things a lot easier on your side as they share the same needs and care requirements. 

That said you can also keep them with other fish that are not aggressive and are around the same size. Fin nippers and highly active fish are not great tank mates for this fish. You will want to pick fish that are calm and swim slowly. 

Considering all of these points, here are our top tank mates for your Goldfish:

Make sure your tank parameters are set to something that all your fish can tolerate. At the same time, you should not keep the smaller fish we mentioned above with larger types of goldfish that can eat them. Most smaller fancy fish have smaller mouths that can not eat small fish like guppies. 

A Group Of Common Goldfish In Aquarium

Conclusion

Goldfish are one of the first fish domesticated by humans. The current goldfish in the aquarium hobby do not look like their old ancestors at all and are much more fragile fish. Yet they are still hardy fish that can tolerate a wide range of water parameters. Goldfish is also one of the most mistreated ornamental fish in the world. These fish are large and you should never keep them in a fish bowl.

References:
Carassius auratus auratus (goldfish)
Carassius auratus
The evolutionary origin and domestication history of goldfish (Carassius auratus)