Species guides Featured Articles

Fancy Goldfish Care

fantail goldfish fancy goldfish

Fancy or Fantail Goldfish are an extremely popular aquarium pet, but there is still a lot of debate on their care, in particular, temperature requirements. In this article we will look through the ideal temperatures for Goldfish to be kept at along with some other top care tips.

Fancy Goldfish

I have seen many debates recently on the keeping of Fancy or Fantail Goldfish, many relating to the temperature that they are kept at along with other topics.

Fancy Goldfish are not a natural occurrence. They have been selectively bred over hundreds of years to create the various forms we see today.

They originate in East Asia, where they were originally bred for their interesting looks and have since been spread all over the world as an extremely popular choice of pet.

fancy goldfish fantail goldfish

Fancy Goldfish – Temperature

Fancy Goldfish were originally bred from Common Goldfish.

Goldfish are thought to be descended from Crucian carp. Fancy Goldfish were bred from Goldfish which displayed certain deformities to eventually create the wide range of appearances we see today.

Common Goldfish are thought of as coldwater fish and many aquarists believe that they should only be kept in outdoor ponds.

This ‘knowledge’ is often transferred across to Fantail Goldfish and it is common to see recommendations to keep Fancies in outdoor ponds too.

Common Goldfish can tolerate a wide range of water parameters and are very hardy.  They will tolerate temperatures as low as freezing and up to 30 degrees Celsius if necessary, but they won’t tolerate the extremes of this range for too long.

Not Coldwater fish!

Goldfish are not coldwater fish. Coldwater fish can only survive in low temperatures. This means that Goldfish are simply adaptable fish that can thrive in various climates.

Goldfish do have a preferred temperature that will help them lead long, healthy lives and it’s much warmer than a UK pond tends to be.

Goldfish’ ideal temperature

Whilst they may tolerate a wide range of temperatures, Goldfish still have a preference.

This may come as a surprise to many, but even common Goldfish prefer slightly warmer water. Studies have shown that the ideal temperature for Goldfish is between 20 – 22 degrees Celsius.

Goldfish originate in the far east where it is thought that much of their lineage traces back to the Yangtze River in southern China. Temperatures here usually vary between 10 – 30°C, a far cry from the freezing temperatures of a British pond.

This makes me wonder why many have decided that this is the only place that they belong.

This follows for Fancy Goldfish, but they fare better in even warmer conditions.

Fancy Goldfish ideal temperature

Fancy Goldfish have been bred for their ‘deformities’, including their short bodies amongst other interesting characteristics.

These desirable looks come at a cost, though, and the Fantail tends to have a weaker immune system.

A weak immune system leaves them more open to illness and infection caused by bacteria in the water.

Reducing bacteria

Studies have shown that water at a temperature in the high 20s holds less harmful bacteria. In turn, this means less risk of the fish becoming ill.

Pure Goldfish states a temperature range of 25 – 27°C as the ideal range for keeping Fancy Goldfish for this reason.

25 degrees is not warm enough to bring any harm to the fish, yet it keeps the water in a healthier state. So if you keep Fancy Goldfish, it may be worth considering an aquarium heater.

This is not to say that Fancy Goldfish will not survive in an outdoor pond. It is certainly possible, the temperature range above is simply deemed the ideal temperature for Fancy Goldfish.

fancy goldfish fantail goldfish

Temperature effects on Fancy Goldfish

Fish are cold-blooded, which means they get their body temperature from their environment.

Different temperatures have effects on fish and many effects are common for all species.

In general, higher temperatures mean a faster metabolism, this means higher growth rates and shorter lifespans.

You may now be wondering: Why are increased temperatures a good idea?

Based on the statement above, the increased temperature of a Fantail Goldfish kept at indoor temperatures will, in theory, make its overall lifespan shorter than a fish kept at cooler temperatures outdoors.

This could mean that whilst the fish lives a healthier life at its optimum temperature, it may not live as long as if it were kept cooler.

Is living a healthy life better than living a longer one?

Effects on Goldfish lifespan

In theory, a Fancy Goldfish in a pond may live longer than a Fantail Goldfish that is kept indoors, this is due to indoor temperatures being higher (faster metabolism) combined with less need for ‘hibernation’.

Goldfish go into a state of dormancy at cooler temperatures, sometimes referred to as ‘torpor’. Koi do this too in winter.

This state of dormancy almost hits pause on their lifespan as they enter a form of hibernation. They will eat infrequently, move very little and even breath less whilst in this state.

Goldfish can enter this state at temperatures from 15 degrees C or below.

This state of dormancy, combined with a slower metabolism may mean a longer lifespan, but the fish will not be active for some of it whilst in a torpor state.

Indoor aquariums without a heater in the UK remain at room temperature throughout the year. This is usually too warm for the Goldfish to enter this dormant state, this would suggest another reason that indoor Goldfish should have a shorter lifespan overall than a Goldfish in an outdoor pond.

The longest living Goldfish

However, contrary to what we have just covered, many of the longest living recorded Goldfish have been kept indoors, some in aquariums that most aquarists would consider far too small for Goldfish.

So maybe this theory of warmer water meaning a shorter lifespan isn’t always the case?

My theory on this is that the warmer conditions meant a healthier life than a Goldfish may have had in the colder conditions of an outdoor pond.

That in turn could outweigh the effects of any increased metabolism.

Benefits of warmer water

Warmer water holds many health benefits. The bacteria count is reduced and the digestive ability of the fish is increased.

Cold water reduces immune function and inhibits fishes ability to digest food.

These two factors alone make for a much healthier life for your Fantail friends if they are kept at warmer temperatures.

Here’s a link to one of the reports on ‘Britains oldest Goldfish’:


Are Goldfish the most adaptable fish?

This goes to show that Goldfish are very adaptable and can thrive in a range of conditions but they often live longer, healthier lives at indoor temperatures.

This combined with the reduced immune system capabilities of the Fantail Goldfish would suggest that warmer water is the optimum for them to live long, healthy lives too.

In optimum conditions, it is said that Fantail Goldfish can live for up to 15 years, depending on species.

Heavily ‘deformed’ species such as Celestials, bubbles eyes and Ranchu tend to have the shortest lifespans.

Fancy Goldfish care

Fancy Goldfish are relatively easy to care for. Whilst they are not as hardy as their slim bodied cousins, they are still fairly resilient.

Some of the most important factors to consider are the eventual size of the fish and the waste they produce.

Fancy Goldfish are often on sale at relatively small sizes, but they grow. A fancy Goldfish, depending on breeding, can reach 8 inches in length but average between 6 and 8 inches when fully grown.

Even at 6 inches in length, that’s a fairly sizable fish when you take into account their height, girth and fin length too!

That means that aquarium size is fairly important, especially when combined with their waste levels.

Whilst they are growing, Goldfish produce a lot of waste, this is due to their ability to consume more food than other species of fish of the same size might do.

It is common for new fish keepers to overfeed their fish, whilst this may mean it goes to waste in some tanks, Goldfish will often eat the lot!

In short, they’re pretty greedy and have very capable digestive systems!

These two factors combined mean that a larger tank is much easier to keep them healthy, but more importantly, filtration needs to be up to the task.

We recommend an aquarium size of 180l (3ft) with a suitable external filter. This allows for plenty of waste dilution whilst providing lots of space for fully grown adult fish.

This size aquarium allows for multiple fish, Fancy Goldfish can be quite sociable but friends are not absolutely neccesary!

2 – 4 Fantail Goldfish should have plenty of space in this size aquarium with adequate filtration.

fancy goldfish fantail goldfish

Fancy Goldfish Aquarium Decor

Aquarium decor is mostly down to personal choice, Goldfish aren’t too fussy, but as with all fish keeping decor needs to be fish safe.

One area to really consider is the substrate. Goldfish in general are notorious for digging around in the substrate. Occasionally they will lodge a piece of gravel in their mouths.

When this happens, it can be very difficult to remove from the fish’ mouth and can lead to an untimely death.

This is a fairly common issue, so when choosing a substrate, I would recommend fine gravel or sand, preventing this problem from occurring.

All other decorations are down to personal choice. But be warned, live plants will be eaten! Goldfish like their veggies!

Feeding Fancy Goldfish

Goldfish are the gannets of the fish world. They will consume just about anything that they can swallow. So feeding them isn’t too difficult.

A varied diet should keep them in optimum condition with the bulk of their diet being a suitable, good quality pellet food, we highly recommend Fluval Bugbites!

The main consideration is how much you are feeding. It is very common for aquarists to overfeed their fish, I do it all the time.

Depending on what food is used, the equivalent of a few pellets per day should be plenty for your fish to thrive. A good timing to work off is as much as your fish will consume in 2 – 5 minutes.

This will ensure that the fish are full but you are never overfeeding too much.

Goldfish are also great ‘beggers’, even on a full stomach, they will often act like they haven’t eaten for days!

For more on Fantail Goldfish care, check out our quick care profile HERE


fantail goldfish

Fantail Goldfish – Summary

Fantail Goldfish are an extremely popular aquarium fish and for good reason!

Their care is easy and they grow into big beautiful fish with big personalities.

The choice of temperature is entirely down to the keeper. Fancy Goldfish will live quite happily at cooler temperatures, but they fare much better in slightly warmer conditions according to many studies.

Aquarium size is important in my opinion, whilst they can be kept in smaller aquariums and have been known to live long lives in such conditions, I feel it is far more appropriate for them to have plenty of space to swim, dig and search for food.

Ultimately, these are fairly large fish as adults that produce a lot of waste as they grow.

For more info, check out the references below!

Happy fish keeping!

Found this useful? Check out the rest of our blog: HERE!


fantail goldfish

Frequently asked questions:


Pure Goldfish

Aquatic Invaders of the Pacific Northwest; Carassius auratus auratus (Common Goldfish) – Martin Safer


Catfish vet

Komiyama T, Kobayashi H, Tateno Y, Inoko H, Gojobori T, Ikeo K (2008) – An evolutionary origin and selection process of goldfish.

About the author

James @Seriously Fishy

I am a fish keeping enthusiast with over 20 years experience. I currently keep American Cichlids (CA) which are my favourite fish to keep so far. I started Seriously Fishy as I noticed a large volume of people on various web pages looking for help with Aquarium basics. I created the first Seriously Fishy book to solve the issue in 28 pages, that led to the Seriously Fishy UK fish forum and blog.

Leave a Comment