How to Take Care of a Goldfish

PetMD Editorial
Written by:
PetMD Editorial
Published: February 11, 2016
How to Take Care of a Goldfish

The common goldfish (Carassius auratus) is easily among the very first fish species to be kept by humans as a pet. If there is an aquarium species deserving of the title “the people’s fish,” this is the one.

While scores of domesticated varieties, developed by highly dedicated breeders, have emerged over the last 10 centuries or so, the iconic goldfish remains instantly recognizable even to those who have never owned an aquarium.

Still, despite their longstanding (traditional, even) use as an ornamental fish, and the countless volumes written about them, the needs of the goldfish remain misunderstood.

Many new pet parents view the goldfish as a low-maintenance pet with minimal needs.

But goldfish require an understanding of basic fishkeeping and have specific needs that need to be met in order to thrive.

Here’s a guide that explains where goldfish came from and how to properly care for them—from goldfish tank setup to goldfish care  and feeding requirements—to ensure they thrive.

History of the Goldfish Pet

Throughout the majority of the time that goldfish have been kept as pets, they have been homed predominantly in ponds.

During the 9th century, many Buddhist monks in China began to keep flashy-colored “chi”—the wild carp ancestor of the goldfish—in ponds in order to keep them safe from predators. (Their flashy gold, red, yellow, or orange scales made them prime targets in their natural habitat.)

In the 1200s, goldfish had become domesticated and completely genetically distinct from their chi ancestors. They were seen as a status symbol for the wealthy and kept in ponds outside their homes.

By the 1500s, it was commonplace to keep goldfish indoors in bowls, although they should never be confined to a bowl.

This practice might have begun for the purpose of showing off one’s finest specimen to guests, with their primary residence nevertheless outside in the pond.

In time, “fancier” varieties were permanently kept inside in fishbowls due to their inability to evade predation or compete with the faster wild-type pond mates outside. As a result, goldfish became genetically distinct from their chi ancestors.

How Long Can Goldfish Live?

While popular depictions of goldfish would have you believe they have a more conservative life span, that could not be farther from the truth.

If housed and cared for properly, a goldfish can live to be 20 years old.

Goldfish Tank Setup

While many people have heard, “goldfish will grow to fit the size of their enclosure,” this is a complete myth.

A goldfish requires adequate living arrangements, just like any other pet.

Here’s how to create the best goldfish tank setup for your new pet goldfish.

Why Goldfish Should Not Be Kept in Bowls

Before you think that bowls are a suitable home for a pet goldfish, the bowls used in the early centuries were not the kind of bowls you might think of. These rather large, ceramic basins were considerably roomier than the cramped desktop bowls of today.

And, because fish in the former instance were truly prized and adored, they likely received far more care and attention than the typically doomed carnival prize goldfish of today.

If truth be told, fishbowls are not appropriate for any sort of aquatic animal.

Goldfish Tank Size 

For the most suitable tank for your goldfish, you should start with a 75- to 100-gallon tank. This may seem large, but, depending upon the breed, the C. auratus can reach lengths of well over a foot at their adult size.

Although the rule of thumb is to start with a tank that contains 20 gallons for every goldfish, as they grow (the goldfish can grow to be 1-2 feet long), you will need to upgrade their tank. So starting at a larger size is your best bet for creating a forever tank for your goldfish.

The larger tank size is also important because goldfish are not known for their cleanliness. Seems like no matter how sparingly you feed them, they are ceaseless poopers.

As these solid wastes break down via natural microbial processes, they inevitably consume precious oxygen and generate toxic metabolic by-products such as ammonia.

A larger tank will also allow you to more easily deal with these issues because:

  • They are more dilute

  • They allow for easier installation of an adequate water filtration system

Goldfish Tank Temperature

Sure, goldfish can survive (at least for short periods of time) in waters ranging from near-freezing to tropical. That does not, however, mean that it’s easy for them to endure daily, steep temperature change.

Goldfish require a heater (set to around 68°F) to ensure temperature stability. But using a larger tank will help to minimize drastic temperature changes due to the large volume.

Water and Filtration Requirements 

Goldfish can generate copious amounts of waste, so you will need a powerful aquarium water filter (such as a properly sized canister filter) and to be diligent about cleaning their tank.

Hang-on-the-back types of filters work great for goldfish but must be greatly oversized to meet the task. The idea is to aggressively filter the water without creating excessively strong, localized water currents (especially for the less athletic fancy goldfish varieties). 

The additional aeration created by an air diffuser (e.g., bubble wand) can help with water circulation and gas exchange. These devises should, however, be used very carefully with certain goldfish varieties (e.g., bubble-eyes).

Goldfish like water where the alkalinity is higher than the acidity, so water with a pH between 7.0-7.4 is best.

Goldfish Tank Decorations

The tank interior, in terms of decoration, does not require extraordinary attention. Pea gravel (as opposed to sand or finer gravels) is best for the substrate, as the fish can more easily avoid ingesting it when slurping bits of food from the tank floor.

Decorative stone, artificial plants, etc., add a nice touch but should be used minimally as to leave the most swimming space.

Live plants can be used only with caution, as goldfish are known to consume all but the toughest or least palatable types (try anubias or java fern.).

Goldfish Food

Diet is also vital for the goldfish.

Goldfish are technically omnivorous, eating almost anything you throw at them, but not all foods are equal here.

Goldfish benefit most from a high carb-to-protein content food. Stick to a quality, specially formulated goldfish diet with occasional “treats” in between.

And don’t overdo it!

Beyond voracious, goldfish simply don’t know how to stop eating and will harm themselves if presented with too much food. Overfeeding can also foul the water and harm your goldfish.

You should only feed your fish what they are able to consume in 2-3 minutes, once or twice a day.

Pre-Soak Your Goldfish’s Food

If you’re feeding your goldfish flaky food, you should pre-soak the food.

Goldfish are natural bottom-feeders, so when the flakes sit on top of the water, it causes your goldfish to gulp. This can upset their swim bladder and equilibrium—causing them to float upside down.

Fill a cup with some water from the tank and swirl around their meal in the water. You can then dump the whole cup into the tank for your goldfish.

Adding Goldfish to Your Aquarium

Goldfish are peaceful fish that tolerate, or even enjoy, each other’s company. That being said, proper stocking is critical for successful long-term care.

To start, don’t overstock.

While the many beautiful goldfish varieties make choosing just a few individuals difficult, remember this: The more heavily stocked the aquarium is, the more time and money you will spend cleaning it.

You should add no more than one fish per 20-30 gallons of tank volume. Add to the community slowly; start with one, and then add one at a time (perhaps one new fish each month) to safely gauge changes in overall tank cleanliness as you proceed.

Following the above guidelines and sticking to top-shelf equipment and foods, you will find that maintaining your goldfish’s health is not as hard as you thought. In truth, if reared in an environment that meets its particular needs, your goldfish just might outlive you.

By: Kenneth Wingerter, Advanced Aquarist

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