Last Updated: 6/16/11

Quick Information
Introduction and Description
Goldfish Longevity
Setup and Water Preferences
Myths About Goldfish

Common name: Goldfish
Scientific/Latin name: Carassius auratus
Maximum length: 6 to 8 inches for fancy varieties; up to 14 inches for regular goldfish
Colors: Gold, orange, white, black, "blue," brown, silver, bronze, red, and more perhaps
Temperature preference: 50 to 75 degrees F, can survive 33 to 100 degrees F for short periods of time, fancier varieties less tolerant of extremes
pH preference: 7 to 8
Hardness preference: Moderate
Salinity preference: 1 Tablespoon per 3 to 10 gallons
Compatibility: Males may tear off females' (or males' if no females to harass) fins or nip her vent; generally ignore other species but may eat small fish
Life span: Average around 10 years for healthy fish but oldest fish ever was 43+ years at death (see below)
Ease of keeping: Easy IF you know what you are doing
Ease of breeding: Easy to moderate IF you know what you are doing

Introduction and Description

Carassius auratus, or the goldfish, is probably the most tortured fish in the world. There are nearly a hundred varieties of goldfish. They are all the same species and can interbreed (although sometimes difficult and not recommended to mix varieties). Goldfish grow large if given proper room and food. Common goldfish with 50+ gallons to swim in, grow easily to a foot long. Lengths of six inches or more for most varieties are not unheard of. Thus, goldfish are absolutely unsuited for life in bowls or small tanks. They are in fact the least suited of most commonly sold fish. If you want a bowl or small tank, keep small tropical fish with a heater or small coldwater fish without one. If you go so far as to desiring no electricity at all, a betta will do well in warm areas and a paradise fish in cooler areas. Even then, anything less than 2 to 5 gallons for a fish or two is cruel in my mind. Bigger is ALWAYS better when it comes to tanks. Bigger tanks are also easier to care for.

If you do not believe goldfish get big, here are photos of my poor dead Jack next to a yard stick. She was a comet I bought in 1996 that died on 9/1/04 in my 1800 gallon pond for unknown reasons (I think she got stuck in the shallows with her mouth out of water). She was 14" long! Jack top view, Jack right side, and Jack left side.

Room per goldfish and temperature preferences and tolerances:

What does it mean that goldfish can live for decades and grow to a foot? Most goldfish keepers believe that for goldfish to thrive, they require at least 10 gallons per fish with more always better. In ponds, 30-50 gallons per fish is better. Goldfish also desire (but do not require) a change in temperatures over the seasons. Outside, mother nature provides this. Inside, either using no heater or setting it in the 50's or 60's degrees F range (60's or more for fancier varieties), provides enough of a change. This seems to make them happy. It also is the key to getting the fish interested in breeding. Above about 75 degrees F, goldfish are unhappy. Never set the heater this high. They can tolerate these temperatures, even into the 90's for a few days, for only the length of a normal hot spell in summer.

Goldfish Longevity

Goldfish have been known to live into their 30's at least. Life expectancies from 10 to 20 years are normal for well-cared for fish. The oldest captive goldfish on record was Tish who is in the Guiness Book of World Records. His owner, Peter Hand of England, won him at the fair in 1956. Tish died the first week of August, 1999 so he was at least 43 years old (probably 44 since most carnival goldfish are about 4 months to a year old). Tish only grew to 4.5 inches long and was silver. Since 4.5 inches is not that long, either Tish was stunted (he spent many years in small bowls before moving into a tank), and/or he was a fancy variety of goldfish. Peter Hand's mother, Hilda Hand, said after Tish's death, "I am very sad....Over the years we have become very close and I could sense if he was happy or not." The oldest living goldfish is also in England. As of 2003, "Goldie" is also 43 years old and will be in the next edition of Guiness.

Setup and Water Preferences

As mentioned above, the larger the tank, the better. I had one small, two medium, and one large goldfish in 50 gallons which worked well. Temperatures from the high 30's to high 80's degrees F are tolerated by common goldfish. Fancy goldfish may die below 50 degrees F (although many overwinter some fancy goldfish outside, and they can survive). All varieties may die above 80 degrees F, actually most likely due to the large decrease in the oxygen carrying capacity of the water at these higher temperatures. Goldfish seem to do best at a moderate hardness. Mine are in soft water. I add one Tablespoon per 5 gallons of aquarium salt (for freshwater fish) to increase the ions in the water and lessen the osmotic differentiation between the fish and its water. (See the salt page for more information.) Goldfish eat just about anything including most flake and pellet foods, live plants (yum, anacharis!), cucumber (cut in half and weighted down), boiled and peeled peas, earthworms, insect larvae, and fish eggs and fry.

Since goldfish are large, they poop a lot. Thus, not only is good filtration and aeration a necessity, but their water should be partially changed EVERY week (with dechlorinator, salt, etc.) in tanks. Change between 25- 50% every week (I know some other aquarists insist that this will kill fish but I do it, and my fish thrive.) on a tank stocked at maximum capacity. This pertains to tanks in the 20 to 200 gallon range. Smaller tanks should change more and larger tanks and ponds only need change small amounts, and less often. In bowls under three gallons, the water may need daily changing. In large ponds, water changes may only be necessary on rare occasions. The amount changed and frequency also depends on how many fish there are, how big they are, what type of filter there is, what the temperature is, and how big the tank or pond is. There really is no exact percentage to be changed at an exact frequency.

Mental and Physical Stimulation:

Aquarists often say that goldfish need stimulation which is why they do poorly in a small bowl or tank. While all fish need stimulation to thrive, goldfish seem to especially need it. Mental or intellectual stimulation arises from having other fish to interact with; things to play with like plants, rocks, etc.; a variety of foods to eat; places to explore; etc. In a tank, to provide the fish with more excitement, about once a month, rearrange the fake plants and ornaments in the tank. Also, provide a variety of foods from flakes to pellets to live foods to frozen to freeze dried. Ponds over a few hundred gallons provide plenty of excitement with new places to explore, live food around every corner, and other fish. Physical stimulation comes from having room to swim, other goldfish to touch, and a chance to spawn. Without both types of stimulation, a goldfish may become ill, swim little, or generally do nothing (act bored or, personifying it, seem depressed).

1. Myth: Goldfish can live happily in a bowl.

Fact: Goldfish may survive in a bowl, sometimes even for years but certainly cannot reach their full potential in a container under 10 gallons. Consider that a mature goldfish may reach 6 to 12 inches, and it is easy to see that such a fish could not even fit in a so-called "goldfish bowl." Keeping any fish in a tiny bowl (even the poor tortured betta) with no physical or mental stimulation leads to a very sad and bored fish (assuming that you believe fish can feel) as well as one prone to illness and weak in strength. Without aeration or filtration in bowls, the water will always be dirty and low in oxygen even with daily water changes. The goldfish will not stop growing to fit the size of the bowl as many people think. The fact is that most bowl-kept goldfish die in their own waste long before they can fill out the bowl but it has happened.

2. Myth: Goldfish are hard to breed.

Fact: Goldfish provided with the right conditions are very easy to breed. In a pond setting, it is impossible to stop them! That is why so many innocent goldfish are sold as "feeder fish." To learn about the cues needed to induce spawning in an indoor tank, visit my goldfish breeding page.

3. Myth: A tank with goldfish will always be filthy and unsightly.

Fact: That is like saying that an infant in diapers is always dirty. The tank is only as dirty as you want it to be. The more water that you change and the more gravel vacuuming that you do, the cleaner the tank is. The better the filtration, the cleaner the tank is. My 50 gallon fish tank was crystal clear year round. I changed half of the water every week. Even a goldfish in a fish bowl could have clear water if half of it were changed every single day.

4. Myth: Goldfish are too "dirty" to live with other fish.

Fact: Yes, goldfish like to stir up the gravel and chew on any live plants. Yes, they poop a lot but not any more than another species of similar weight. If the filter is strong, the tank has few live plants, and the water is changed weekly using a gravel vacuum, the tank should be just as clean as one containing another species. Other species may not be compatible with goldfish for reasons listed on my goldfish care page two but not because goldfish are dirty.

5. Myth: Goldfish are stupid, boring, and/or ugly.

Fact: Well, this is more of an subjective assessment. I find my goldfish to be both gorgeous and highly intelligent as well as entertaining to watch. Most of the enjoyment comes from watching the goldfish interact with one another.

Go to Goldfish Care Part Two.

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