Although fancy varieties have become increasingly popular over the years, the no-frills common goldfish is still what many people would first picture if they were asked to think about a goldfish.
They may not have the flowing fins or unusual body shapes of their fancy counterparts, but commons are generally very hardy and healthy, making them ideal for beginner fish-keepers. That said, many advanced aquarists still can’t resist their charms.
In this guide, we take a detailed look at the common goldfish. We start with a summarized table of all the most important care tips and stats of their breed profile, before moving on to fleshed out details of their history, characteristics, and many aspects of the care routine required to successfully keep them in a home aquarium.
By the end of this guide, all the details on this fish will be ‘common’ knowledge to you 😉
Contents - Click to Jump to Section
Breed Profile and Summarized Care Tips
|Common name(s):||Common goldfish|
|Scientific Name(s):||Carassius auratus|
|Care Level:||Easy to Intermediate|
|Temperament:||Peaceful and social|
|Adult Size:||10 to 12 inches (and occasionally more!)|
|Color Form:||Various solid, bicolor and combinations of red, orange, yellow, white, black. Mostly metallic orange or orange and white.|
|Lifespan:||10 to 15 years. 20 years+ is not unheard of.|
|Minimum Tank Size:||40 gallons, bigger is better, prefer to be in a pond.|
|Typical Tank Setup:||Strong and efficient filtration, preferably planted, sand or gravel substrate to dig into, with good lateral swim space, so preferably wide tank, rather than tall.|
|Tank Level:||All over|
|Water Conditions:||Freshwater, 65-75 degress fahrenheit, KH 4 to 20, pH 6 to 8|
|Tank mates / Compatibility:||Other single-tail goldfish, invertebrates, koi, minnows, african dwarf frog, other 'pond species.'|
T%hey are the type that most resemble their wild carp relatives.
They have flat and elongated bodies that are largest in the middle and taper from their back and belly forward toward their snout, and backward toward the base of their caudal fin.
Their caudal fin is short, erect and forked, nothing like the long, flowing tails of many fancy goldfish varieties.
What Colors can They be?
You might be picturing a classic orange goldfish, but they come in a wide range of colors.
As well as that striking orange shade, they can be white, yellow, red, brown or black. Sometimes they’re just a single solid color, but they can have more than one hue on them in a patchy or somewhat spotted pattern.
How Big is a Fully Grown Common Goldfish?
They can grow surprisingly large, but it all depends on the size of their environment.
Many are kept in tanks too small for them and tend to grow to an average of 4 inches. However, if you keep them in an appropriately sized tank (about 40 gallons+, but more on that later), their average length is closer to 7 or 8 inches.
However, if kept in a pond or very large tank, they can reach well over a foot.
How Long do They Live?
When looked after properly, they can live for a significant amount of time. The average lifespan of a well-kept goldfish is around 10 to 15 years. Although, they have been known to live for over 40 years.
However, the sad fact is that many people don’t bother to look after them properly and many of them live for just a couple of years or less.
History and Origins
All goldfish are descended from wild carp, but commons are the most similar to their wild brethren.
They descended from the Chinese Crucian carp, which was known to locals as “Chi.” In the wild, they’re a silvery gray color, but genetic mutations sometimes caused Chi to turn out red, orange or yellow.
As early as the 9th century, people started to keep Chi in ponds, so the brightly colored mutations were safe from predators and became more common (in the wild, they would have been eaten right away, as they lacked camouflage).
People kept ponds of colorful Chi for several hundred years, but it wasn’t until around 1240 that they became tame and developed into a species distinct from the Chi – something more akin to the common goldfish we know and love today.
Goldfish increased in popularity in the 1500s, when people started to keep them in bowls, and things have only progressed from there.
Today, they are perhaps the most ubiquitous pet fish species in the world.
Easy or Hard to Keep in a Home?
They are fairly easy to keep in a home aquarium, being much hardier than even their fancy goldfish relatives.
In fact, they’re seen as so simple to keep that they’re the first type of fish that many people own.
However, it’s worth pointing out that they do need a little more thought and attention than some people provide for them. You can’t just put them in an aquarium and leave them be.
Common Goldfish Care Needs
They are relatively low-maintenance and don’t have extra requirements beyond the general requirements of keeping most goldfish. So check out that link, it has all the info you need!
How to Feed Them
From your past expereinces, you might think that all they need to eat is basic flake food, but that’s not the case at all. Just like most creatures, they thrive on variety and need to eat a range of foods to get a nutritionally balanced diet – imagine how you’d be feeling if you were fed cornflakes for every meal!
They are omnivores, meaning they eat a range of plant and animal foods. It’s a wise idea for the bulk of their diet to be a high-quality pellet or flake food that’s specially designed to meet the nutritional needs of goldfish.
However, you should also occasionally feed them some more varied foods, such as brine shrimp, shelled peas, chopped boiled vegetables, and bloodworms.
Goldfish don’t have stomachs, so it’s best to feed them foods that are relatively easy to digest and to feed them several small meals a day rather than one large meal.
If overfed, they can (and will) eat themselves to death, so be very careful not to feed them too much at once.
Getting the right tank set-up is the key to helping them live a long, happy and healthy life. Let’s see how to achieve this.
Size and Shape of Tank
Common goldfish get much larger than fancy types, and they need an aquarium of sufficient size.
As per the info in our goldfish tank size guide, the minimum tank capacity you should go for is 40 gallons. However, we’d recommend starting with at least a 40-gallon tank, and larger if you have room.
For each additional common you keep, add 10 gallons to your initial tank size. So, for two commons we’d recommend a tank of at least 50 gallons, for three we’d recommend 60 gallons, and so on.
Due to their size when fully grown, and their love of high activity and fast swimming, it’s unfair to keep them in too small a tank. What’s more, they produce a lot of waste, so if you had a small tank you’d need to constantly clean it to keep decent water quality.
Ideally, select a tank that’s wider than it is tall. This means there’s more surface area to the water and more oxygen can penetrate.
Do they Need a Filter?
Some people don’t realize this, but commons should always have a filter in their tank. They produce a lot of waste, including hefty levels of ammonia, so proper filtration is a must to avoid polluted water.
To keep up with the high demands of all that waste, look out for a high-quality filter that turns over around 10 times the volume of the water in your tank every hour.
A smooth gravel substrate is great for common goldfish, as it will allow them to exhibit natural foraging behaviors, as they look for food between the pebbles.
When you cycle your tank, colonies of beneficial bacteria will build up in the substrate, too, helping to maintain a healthy tank.
Do they Need Lights?
They like to have a decent amount of light. However, they shouldn’t be kept right in direct sunlight, as this can cause their tank to get too hot and can encourage algae growth.
If the position they’re kept in gets an adequate amount of natural light, they should be fine without lighting.
But, if they’re kept in a shaded spot or a gloomy tucked away corner, get a light for the hood of your aquarium and switch it on and off in a way that simulates a natural day-night cycle.
What temp Should Their Water Be?
They are a hardy fish, they can survive at extreme temperatures, but that doesn’t mean they should. Water that’s too hot or too cold will be uncomfortable for them and could stress them. They can even die from sudden drastic changes in temperature.
The optimum water temperature Is between 65 and 72 degrees Fahrenheit.
While most heated houses should be able to maintain this temperature all year round, it’s not a bad idea to have a basic water heater as a backup, just in case of an emergency, like a breakdown of your central heating.
Preferred Tank Mates
They are temperate fish – preferring cooler water – so they can’t be housed with tropical fish, so that rules out many species. In fact, the best tankmates for them are other goldfish. However, you should be careful not to house them with slower swimming varieties, as they will out-compete them for food being such super fast swimmers and movers.
Other tankmates you can consider are snails and shrimp, african dwarf frogs, and other fast swimming, similarly sized pond fish.
All this said, they are quite social, so it’s nice to keep more than one together or to give them some company, but be sure not to overcrowd them.
Video: A Close Look at the Common Goldfish
Here’s a closeup look at a couple of beautiful commons in action. They could definitely do with a bigger tank, but they’ve been set-up for spawning, so hopefully, they usually have a larger and more enriching environment to live in.
Common goldfish do make a great fish for the beginner, but they’re not as simple to keep at home for as you might initially believe.
If you don’t have room to provide them with a large tank, then this variety is just not for you.
But, if you do take into account their needs and put in the proper attention they require, you could have a fish-friend for the next 10 or 20 years!
Happy fish keeping!