Goldfish: Species Profile

Category: Goldfish

Common Names: Goldfish

Scientific Name: Carassius auratus

Family: Cyprinidae

Minimum Tank Size: 15 Gallons

Care Level: Easy

Temperament: Peaceful

Max Size: 12+ inches

Temperature: 65-75 F

pH: 6.5-7.5

Tank Level: All

Colors: Orange

Diet: Omnivore

Breeding: Difficult

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Goldfish Species Overview

Goldfish are a popular choice for tropical fish tanks because they come in many colors and shapes. They’re also hardy, meaning if you forget to clean your tank for one too many days, it’s unlikely you’ll find them belly up.

Furthermore, goldfish are social creatures. Therefore, they thrive off the company of goldfish companions and are generally docile with other fish.

Because goldfish are a low-maintenance fish, they’re an excellent choice for people new to caring for tropical aquariums.

Distinguishing Features

“Goldfish” is a generic term for this species that contains hundreds of varieties. In nature, it’s common to encounter goldfish ranging from a gold color to cream.

However, there tends to be more variety in captivity, given that breeders have been able to draw out specific color genes. Some of the most common goldfish colors you’ll encounter include:

  • Yellow
  • Orange
  • Red
  • Black
  • White
  • Brown

In some cases, goldfish come in solid colors. But many other times, you can pick from multi-colored fish, giving your tropical fish tank a unique and colorful flare.

Goldfish in aquarium

Basic Characteristics

Although there’s a massive diversity in goldfish in terms of their size and appearance, most types within this species share the same primary characteristics. They include:

  • Pharyngeal teeth
  • No scales on their head
  • No barbels on their upper jaw
  • Two sets of pelvic and pectoral fins
  • Three single fins (anal, dorsal, and caudal)
  • 27 to 31 scales on their lateral lines

Additionally, most goldfish have big eyes, sometimes disproportionate to their head. They also tend to have an excellent depth of hearing and smell, although these aren’t items you can notice by looking at them.

Goldfish Variations

Of the hundreds of goldfish varieties that exist, most fall under the “single-finned” or “fancy” categories. But even many single-finned goldfish look fancy to the passerby.

Below are some of the many types of goldfish you can choose from when choosing them for your tank.

Common Goldfish

The single-finned common goldfish has a slender, long body. Despite their attractive colors, these are the bottom-of-the-barrel type of fish, for many people use them as feeder fish.

They’re hardy fish, surviving in temperatures below zero and over 90 degrees Fahrenheit.

goldfish carassius auratus

Wakin Goldfish

People commonly confuse the Wakin goldfish with koi fish, as they can grow up to 19 inches long. Wakins have a double tail, although they still belong to the single-finned group of goldfish.

Bubble Eye Goldfish

The bubble eye goldfish will attract the “eye” of anyone passing by them. These fancy goldfish have fluid-filled sacs, causing their cheeks to bulge and their eyes to pop.

Telescope Goldfish

Telescopes are another type of fancy goldfish with massive eyes protruding from their heads at a forward angle. They have long, double fins and round bodies, making them steal the show of many tropical fish tanks.


Goldfish originate from the crucian carp in China. Traditionally, these carp had a grey or silver color.

However, during the Chinese Jin Dynasty starting in AD 265, people started noting that these fish had red scales. Over the next few hundred years, the Chinese began hand-selecting and breeding these red carp and kept them as ornamental fish in ponds.

Over time, the yellow goldfish emerged, and it became such a sacred fish that the Song Dynasty forbid commoners to raise them.

Goldfish made their way to Japan and Europe in the 17th century before going to North America around 1850. To this day, they continue to be a popular choice for adding color to tropical fish tanks.

In their natural habitat, goldfish live in freshwater with slow movement. They prefer sludgy water, given that ponds are their ideal environment.

For this reason, goldfish love muddy bottoms, although most fish owners understandably balk at the thought of this.

Goldfish also love living where there are many live plants, as they enjoy eating and hiding in them. Some of the goldfish’s favorite plants include:

  • Java fern
  • Crypts
  • Onion plant


There isn’t a one size fits all situation when comparing the length of goldfish. On average, goldfish range from seven to over 16 inches long. They also typically weigh between 0.2 – 0.6 pounds.

However, the longest goldfish on record clocked in at 18.7 inches. Furthermore, you can sometimes find goldfish weighing five pounds in the wild.

The ultimate size your goldfish will grow to depends on its species, nutrition, and sex.

In most cases, female goldfish are longer and rounder than males. Such a size difference is especially notable during spawning when females puff out their vents and males tuck theirs into their bodies.

The bottom line is to ensure you speak with whomever you’re purchasing your goldfish from so that you have an idea of how big they’ll likely grow. That way, you can buy a tank that they can grow into.


Goldfish are notorious for their long lifespans, meaning you can expect them to outlive many other fish species in your tropical tank.

You can expect your goldfish to live for around a decade at a minimum.

However, if you offer them exceptional care and a stress-free environment, some goldfish in captivity can live as long as 25 years.

Generally speaking, goldfish that live in captivity in ornamental ponds live longer than those in tropical fish tanks, and both of these captive fish average a higher lifespan than those in the wild.

In fact, there are reports of some captive pond-dwelling goldfish living as long as 43 years.

Fancy Goldfish in front of Waterfall


Female goldfish can lay as many as 1,000 eggs at a time. So, if you don’t want to raise dozens of baby goldfish, it’s crucial to know how to tell the difference between males and females.

One of the easiest ways to tell the sex of goldfish is by observing them during spawning. Spots will show up on the gills and pectoral fins of males, while females will develop a swollen vent beneath their tails.

Of course, you likely don’t want to get to this point.

It’s more challenging to tell the difference between male and female goldfish when it’s not mating season. However, males have an anal fin that’s closer to their tails.

Males are also almost always skinnier and more slender than females, whereas females boast a rounder abdomen.

In most cases, you’ll need to wait until goldfish reach sexual maturity, which is around one year old before you’ll be able to tell the difference between males and females.


Goldfish are peaceful fish that get along well with most other types of fish. Furthermore, they’re social, so they’ll appreciate being in a tank with at least one other fish of their species.

In the rare circumstance that a goldfish becomes aggressive, it’s likely because another fish provoked them. They might lash out at this fish, chasing them around the tank to show them who’s boss and prevent future troubles.

That said, of the two sexes, male goldfish have a higher tendency to show aggression than females.

Tank Parameters

Although goldfish are relatively hardy, they still require several specific tank parameters to live a long and healthy life. So, before you purchase your first goldfish, ensure you have the following items ready.

Minimum Tank Size

Since so many species of goldfish exist, the tank size you’ll need varies according to the type of fish you have. However, as a general rule, you should aim to purchase a tank with the following dimensions for an adult-sized goldfish:

  • Height: Three times the body length
  • Length: Four times the body length
  • Width: Two times the body length

Of course, the size of the tank alone isn’t enough—it’s essential to fill it almost to the brim with water. That way, your goldfish will be able to fully take advantage of their space, and there will be plenty of oxygen for them.

Although the gallons of water you’ll need for your goldfish ultimately depends on their adult size and the number of fish you have, you should typically aim to purchase a 50-gallon or larger tank, though your goldfish can thrive in smaller spaces when they are younger and smaller.

Water Parameters

Goldfish aren’t very picky with their water parameters. So, they’re a great fish to add to a tank when you have another species of fish that requires a tighter range of water parameters.


Common goldfish have an impressive ability to withstand a range of temperatures, from freezing temperatures to 90 degrees Fahrenheit. As long as they have access to enough oxygen, particularly if a pond doesn’t fully freeze over in ice, they’ll often survive these ranges.

However, we’re not recommending that you keep your tropical fish tank at these extremes. Instead, aim to keep the temperature between 68 and 74 degrees Fahrenheit.

Furthermore, the fancier varieties of goldfish may die if the water drops below room temperature. Examples of fancy goldfish requiring more careful temperature monitoring include:

  • Orandas
  • Ranchus
  • Lionheads
  • Veiltailes

The good news is that if you have other species of fish in your tank requiring a more specific temperature, your goldfish will often acclimate to it.

As with any fish species, you should never drastically change your tank’s water temperature over a short period of time. Doing so could cause your goldfish to go into shock and die.

Gold fish or goldfish floating swimming underwater in fresh aquarium tank with green plant. marine life.


Goldfish aren’t picky about the water’s pH. They can survive in pH levels between 5.0 and 9.0, although 6.5 – 8.4 is their ideal range.

As with water temperature, you should take care not to change the pH of your goldfish’s water too drastically. Otherwise, they could fall ill and may even die.


Although goldfish are freshwater fish, they still need salt to maintain their health. Salt plays a similar role for them as humans, for it helps them maintain enough electrolytes.

Ensuring your tank’s water maintains salinity can also help your goldfish heal faster if they fall ill.

So, we recommend adding one tablespoon of aquarium salt for every five gallons of water in your tank. Alternatively, you can sprinkle one tablespoon of sea salt for every five gallons.

Tank Setup

Setting up your tropical fish tank is one of the most fun parts of welcoming goldfish into your home, especially if you have kids. Although goldfish are relatively easygoing with their tank parameters, follow our advice below to keep them happy with their tank setup.


A goldfish’s ideal substrate is mud. However, we’re not about to tell you to dig up some mud from your backyard pond and pour it into your tank.

Instead, offering your goldfish a smooth, fine substrate will keep them happy.

Note that goldfish are foragers, so they enjoy pushing substrate around to look for food. Unfortunately, this can lead to injury if your tank’s substrate is sharp.

Therefore, if you have crushed glass gravel or another jagged substrate, remove it from the tank before introducing your goldfish.


Goldfish love having items to hide behind and explore, so feel free to use decorations in their tank. However, the decorations must have smooth surfaces.

That’s because many types of goldfish have long fins that could get caught on rough decorative surfaces. Some goldfish also have natural fluid-filled sacs that can rupture if they have a run-in with a sharp surface.


You should always include plants in your goldfish’s tank for two reasons:

  1. They’re a natural food source.
  2. It gives your goldfish something to hide in.

Since goldfish, especially small varieties, are towards the bottom of the food chain, it’s common for them to feel stressed if they don’t have a place to hide.

So, plants provide a natural space for them to get out of the way of other fish, even if you know the fish in their tank won’t eat them.

Red Blood Parrot Cichlid in aquarium plant green background. Goldfish, funny orange colorful fish


You should keep your goldfish on a day and night light schedule. That way, it’ll mimic the light they’d receive in nature, helping them to know when to feed and rest.

Proper lighting is also beneficial to goldfish because it helps youngsters with their eye development. Furthermore, it’ll help keep your live plants healthy so that they can hide and feed on them.


A filter is crucial for any goldfish tank, given that these fish produce lots of waste since they eat so much.

So, a filter will prevent ammonia and nitrate from building up in the tank water, both of which are deadly to goldfish. It’ll also ensure the water remains rich in oxygen.

Alternatively, you can use air stones if your mechanical and biological filters don’t offer water circulation.


Goldfish typically don’t need heated water, given that most species can survive in a wide range of temperatures.

Nevertheless, people commonly use heaters in their goldfish tanks if they have other tropical fish requiring a specific, warm temperature range.


Goldfish have an omnivorous diet in the wild, meaning they eat a combination of plants and animals. Some of their sources of protein in the wild include:

  • Crustaceans
  • Mosquito larvae
  • Detritus
  • Zooplankton

Most fish owners commonly feed their goldfish flakes or pellets. These are an acceptable option, as long as they’re for goldfish.

Nevertheless, to give your goldfish a boost of nutrients and increase their happiness, it’s also a nice idea to offer them natural sources of protein. You can find these protein sources in pet stores.

Examples of protein-rich food you can feed your goldfish include:

  • Bloodworms
  • Brine shrimp
  • Daphnia
  • Dried Tubifex worms

Your goldfish will also appreciate natural vegetable sources, especially if you don’t keep live plants in your tank. Placing some pieces of lettuce or non-salted boiled peas in your tank are excellent options.

The ideal amount of food to give a goldfish is what they can consume in a 2 – 3-minute period over the course of one to two times per day. Their needs will change as they grow, so you’ll need to adjust the food you give them until they reach adulthood.

It’s best to remove any uneaten food after two to three minutes pass to avoid excess waste in your tank.


Breeding goldfish is easy, given that they spawn in tank environments. In the wild, these fish have set spawning cycles.

But in their artificial tank environment, they’ll spawn sporadically.

You’ll know when your goldfish laid eggs because you’ll see them attached to plants and the side of the tank. Assuming that these eggs underwent fertilization from a male goldfish in the tank, you can expect the eggs to hatch within 48 – 72 hours.

That said, it’s common for goldfish and other fish to dine on the eggs. So, we recommend taking out the plants and toys that the eggs cling to and placing them in a separate tank.

It’s crucial that the tank you put them in has the same water parameters as to where they came from to avoid killing the baby goldfish-to-be.

Please note that you should never release goldfish into local bodies of water. Since they’re native to Asia, goldfish are an invasive species elsewhere in the world.

Goldfish are also prolific breeders, meaning that they commonly take over ponds, crowding out native species.

A green beautiful planted tropical freshwater aquarium with goldfish

Common Diseases

Goldfish are hardy, but they’re not invincible. So, below are some of the most common diseases you may encounter as a goldfish owner.

Swim Bladder Disease

Swim bladder disease gets its name because goldfish lose their equilibrium when they have it, causing them to swim sideways or upside down.

There’s no single cause of swim bladder disease, but it usually relates to your fish’s diet. Below are some of the most common reasons your goldfish may develop this condition:

  • Poor quality food
  • Eating too much
  • Not enough fiber
  • Dry pellets stuck in the digestive tract

To treat swim bladder disease in goldfish, feed them vegetables and other low-protein food. Frozen peas are an excellent option.


Ich, which people sometimes refer to as white spot disease, is a parasitic infection. It gets its name because goldfish itch themselves on whatever objects they encounter in the tank.

Most ich parasites enter an aquarium via newly introduced fish. Goldfish with high immune systems can often fight off these parasites, but if you have a stressed fish, it’ll fall victim to itch.

You can spot ich by looking for tiny spots of white on your goldfish’s scales. Treating ich early is crucial, and you can do so by treating the water with ich medicine that you can purchase from a pet store.

Fin Rot

Fin rot is a painful scenario to watch, as this bacterial infection eats away at your goldfish’s fins or tail.

More often than not, fin rot is a reaction to your goldfish already being stressed from a different aliment. Poor water quality, an overcrowded tank, and sudden changes to the tank parameters are other causes of fin rot.

To treat fin rot, start by changing the water and adding one teaspoon of aquarium salt for every gallon of water. You can also try commercial treatments.

After your goldfish shows signs of beginning to heal, remove 25% of the salty water and replace it with new water. Then, continue with your standard water changes.

Potential Tank Mates

Goldfish are docile fish, making them a good fit for combining with many other fish species, including other goldfish varieties. In nature, goldfish tend to stick together, forming schools.

For this reason, you should ensure that your goldfish has at least one other tank mate.

When choosing potential tank mates for your goldfish, keep in mind that it’s best to combine fish of similar size and agility. Therefore, it’s best to avoid pairing a large, heavy goldfish species with a speedy species like the comet and shubunkin.

Because goldfish have a calm demeanor, it’s best to keep them away from playful and fin nipping fish.

Some of the many species of fish that goldfish get along with include:

  • Platy fish
  • Rosy barb
  • Giant danio
  • Holpo catfish
  • Bristlenose pleco

Furthermore, you can include non-fish species in your tropical tank with your goldfish too. Some excellent options include:

  • Cherry shrimp
  • Hillstream loach
  • Mystery snail

Remember, the more tank mates you give your goldfish, the larger the aquarium they’ll need to accommodate everyone.