Goldfish Care Sheet

Goldfish Species Overview

Goldfish are one of the most recognizable types of pet fish. This care sheet outlines basic care needs for a variety of goldfish species, including: 

• Fantail 

• Oranda 

• Black Moor

• Ryukin 

• Pearlscale 

• Wakin 

• Ranchu

• Tosakin 

• Bubble eye 

• Shubunkin 

• Comet

A common misconception is that goldfish “grow to the size of their tank.” However, goldfish continue to grow throughout their lifetime and can become quite large when cared for properly. Other fun facts about goldfish include:

• Goldfish need a tank with strong filtration because they produce more waste than similarly sized fish. 

• Goldfish are incredibly social, and they can recognize their pet parent over time.

• Goldfish are slow swimmers, and they like calm, slow-moving water.

• With time, goldfish may readily accept food from their pet parent’s hand.

Goldfish Characteristics 

Difficulty of Care	Beginner
Average Lifespan	30+ years with proper care
Average Adult Size	1–18" long, depending on species
Diet	Omnivore
Minimum Habitat Size	20+ gallons for juveniles
Water Temperature	65–75 F
pH	6.5–7.5

 

Goldfish Supplies

Have these basic supplies on hand to care for a goldfish: 

• Appropriate-sized aquarium 

• Appropriate food, dry and frozen 

• Decor 

• Full spectrum lighting 

• Live plants 

• Artificial plants 

• Water conditioner 

• Filter 

• Water test kit 

• Aquarium hood/cover 

• Aquarium net 

• Thermometer 

• Freshwater substrate 

• Heater 

• Airstone 

• Air pump 

• Airline tubing 

• Check valve 

Fish Tank for Goldfish

Goldfish can be housed in aquariums or ponds. At a minimum, a single juvenile goldfish needs a 20-gallon habitat or larger.

You will need to increase the size of your goldfish fish tank as their pet grows. As a rule of thumb, goldfish need at least 5 gallons of tank space for every inch of body length. 

All fish tanks for goldfish should be secured with a tightly fitting lid to prevent escape. Always provide the largest habitat possible, as water parameters are less stable in smaller tanks. 

Which Other Fish Can Live with Goldfish?

Goldfish can be kept alone or in schools in a large enough tank or pond. The size and number of fish you wish to fill your tank with will determine how large the tank should be.

Goldfish can also share a tank with cold-water community fish that are tolerant of lower temperatures, including white cloud minnows, zebrafish, and other goldfish. 

New tank mates must be introduced into an aquarium gradually, and pet parents should remember that their tank’s ammonia, pH, and nitrate levels will change when a new fish is introduced. These parameters need to be monitored carefully after adding new fish.   

Fish should not be kept in overcrowded aquariums, because these conditions often lead to stress and disease in the tank. 

Goldfish Tank Filtration 

A filter system is an essential addition to any aquatic habitat. In addition to keeping tanks clean, filters remove harmful toxins like ammonia from the aquarium's water and add oxygen to the water so fish can breathe.  

Power filters (also known as “hang-on-back" filters) and external canister filters are recommended because they offer effective mechanical, biological, and chemical filtration and do not take up any space inside an aquarium. Generally, goldfish prefer water with slow to moderate circulation. 

Tip: An aquarium’s filter should be powerful enough to process all the water in the tank at least four times an hour. For example, a 20-gallon tank should ideally have an aquarium filter with a flow rate that’s at least 80 gallons per hour (GPH). If a 50 or 100 GPH filter are your only options, pet parents should always size up and purchase the 100 GPH option. 

Goldfish Water Health 

Test your aquarium’s water regularly to ensure its temperature, pH, ammonia, nitrate, and nitrite levels are stable and within a safe range. An aquarium test kit can be used to measure key water parameters quickly and accurately. 

Goldfish Water Temperature

Goldfish should be kept in water temperatures between 65–75 F. They thrive in cooler environments, and they are not suited for tropical aquariums. A goldfish’s water temperature should not fluctuate more than +/- 2 degrees in 24 hours. 

Do Goldfish Need a Heater?

Install an aquatic heater that’s controlled with a thermostat to keep the water’s temperature in the ideal range, especially if you live in a cooler climate or experience colder seasons.

An aquarium thermometer should be used to check the tank’s water temperature daily. 

When selecting a heater for goldfish, pet parents should keep a few things in mind: 

• Some modern heaters have built-in thermostats, while others need to be paired with a thermostat that’s purchased separately. 

• As a rule of thumb, aquarium heaters need between 2.5 and 5 watts of power for every gallon of water in a tank. This means that a 10-gallon tank needs a 25- to 50-watt heater. 

Larger aquariums with a tank volume over 50 gallons may need two small heaters, placed on opposite sides of the tank, to prevent cold spots from developing in the water. 

Goldfish Tank Decor

Note: Goldfish are slow-moving and not particularly mobile. So be sure that their tank isn’t crowded with too much decor and they have lots of open swimming space. 

Substrate

The bottom of a goldfish’s tank should be lined with 1–2 inches of freshwater sand, gravel, or pebbles. Be sure to rinse the substrate with clean, running water before adding it to the tank. Avoid gravel that’s small enough for the fish to swallow. 

Goldfish can survive in a “bare bottom” tank without any substrate, but it helps enrich the fish’s environment and creates more surfaces for the good type of bacteria to grow. 

Aquariums need about 1.5 pounds of substrate for each gallon of water in the tank. For example, a 10-gallon tank will require about 15 pounds of substrate to create a 1- to 2-inch layer. 

Hiding Decor

Goldfish need plenty of hiding spots in their aquarium to feel safe and secure. All goldfish decor should be rinsed thoroughly before being added to the tank. 

Plants for a Goldfish Tank

Plants for a goldfish tank should include live or artificial plants, which will also create hiding spaces in the habitat. 

Goldfish are known to eat any plants in their habitat, so look for hardy plants like anubias, Java ferns, and hornworts. 

Plants should be well-secured in the tank’s substrate to prevent them from toppling over and injuring a fish. 

How To Clean a Goldfish Tank

Pet parents can take good care of their goldfish’s tank by performing routine water changes (no more than 10–25% of the aquarium’s total water volume) every two to four weeks.

When cleaning a goldfish tank, newly added water should be conditioned, at the same temperature, and have the same salinity (salt concentration) as the existing water in the tank. 

Uneaten food should be removed from an aquarium daily with the help of a fine mesh net. 

Draining and replacing the aquarium's entire water volume should be avoided, as doing so will remove the beneficial bacteria in the tank that keep the habitat’s ecosystem healthy. 

Most aquariums will need a full cleaning once a month, depending on the number of fish/invertebrates in the tank.

Goldfish Food

Goldfish should be fed a mix of flakes, pellets, frozen, and freeze-dried food. Look for foods that are specifically formulated for goldfish, as they require more carbohydrates than other species.

To stay healthy, goldfish need variety in their diet and should not be fed the same food every day. 

How Often Do You Feed Goldfish?

Depending on the size and species, goldfish need to be fed small amounts of food once a day and should not be offered more food than they can consume within one to two minutes. 

Goldfish will eat when they are offered food, even if it means overeating to their detriment. Overeating cause serious health issues and an increase in waste production, which can cause an increase in ammonia levels in the tank.

“Sinking” diets will help prevent goldfish from consuming too much air while eating, which can lead to bloating and buoyancy issues. Sinking pellets are hard pellets that gradually sink and settle on the bottom of the tank if they are uneaten.

Goldfish Care Tips

To keep your goldfish healthy, keep these tips in mind when it comes to their habitat.

After a new fish or new equipment is added to a goldfish fish tank, it’s important to test the tank water’s quality once a week for at least two months to ensure that its pH, nitrite, ammonia, nitrate, carbonate, and general hardness levels are in the ideal range.

If the tests’ results are safe and consistent after two months, pet parents can decrease water testing to once a month. Water test kits expire and should be replaced yearly.

Pet parents should monitor their goldfish fish tank and top it off as needed. Before adding new water to the fish tank, the water must be treated with a water conditioner to remove toxic chemicals like chlorine, chloramines, and heavy metals.

A goldfish tank’s filter, water temperature, and other equipment should be checked daily to ensure they’re working properly. The filter should be replaced monthly or rinsed in old tank water during water changes, depending on the water condition and the number of fish in the tank.

Pet parents should follow the use, care, and maintenance instructions provided by the manufacturer of their filter system.

Do not use hot water, bleach, or chemicals while rinsing filter media. This will kill the beneficial bacteria that helps keep aquatic habitats safe, clean, and stable.

Avoid replacing all the filtration media in an aquarium at the same time, as this can also remove beneficial bacteria from the tank. Uneaten food should be removed from an aquarium daily. Food can be removed with a fine-mesh fish net or siphon vacuum. 

Goldfish Veterinary Care

Annual Care

In a properly maintained tank of appropriate size, in which you perform weekly or biweekly water changes and biweekly or monthly water quality tests, it is OK to use a veterinarian only if there is a problem with your goldfish.

However, annual or biannual examinations with a certified aquatic veterinarian are most ideal. Some aquatic veterinarians will even perform telehealth video consultations.

While you can transport your goldfish to a vet, it is recommended that you find an aquatic veterinarian who can make a house call, to avoid transportation stress of your fish.

When to Call a Vet

• Decreased appetite

• Increased lethargy

• Fin tears or rips

• Abnormal swelling, growths, or white/red spots

• Pale gills or gill color changes

• Buoyancy issues

• Distended belly

• Increased respiratory rate

Common Illnesses in Goldfish

• Buoyancy disorders

• Polycystic kidney disease

• Neurofibromas, aka warts

• Parasites such as ich, aka white spot disease

• Fin rot

• Fungal infection