Pearlscale Goldfish: Curious and Fascinating Tank Additions

Charlie Morton

Charlie Morton


Pearlscale Goldfish

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Pearlscale goldfish are famed for being one of the roundest of all fancy goldfish varieties. But this pronounced deformity has led some animal welfare advocates to question the ethics of keeping fish whose traits could affect their health and well-being.

In this guide, I’ll explore some of the issues with keeping pearlscale goldfish and share with you the best practices in keeping them if you do decide to buy one.

Pearlscale Goldfish at a Glance

Pearlscale Goldfish Info
Other Common NamesPing-Pong goldfish
Scientific NamesCarassius auratus
Adult Size6 - 8 inches
Minimum Tank Size20 gallons (75 liters) or more
Tank LevelBottom
Lifespan10 - 15 years
DietOmnivorous - Flakes, pellets, live, and frozen foods
BreedingEgg layers, may require a separate breeding tank
Care LevelBeginner
Water pH6.0 - 8.0
Water HardnessSoft to moderately hard
Water Temperature65°F - 78°F (18°C - 26°C)

Species Overview

Since pearlscales are a type of fancy goldfish, let’s first get to grips with what a fancy goldfish is.

Origin of Fancy Goldfish

Kept in captivity for the past 2000 years, goldfish are perhaps the oldest pet fish in the world. Much like domestic dogs, they’ve been bred into hundreds of different varieties over several centuries, resulting in a bewildering array of forms and colors.

Goldfish breeds can roughly be divided into two types:

  • Single-tailed varieties such as ‘common goldfish’, comets, and shubunkins.
  • Double-tailed, aka. Fancy goldfish, like Ryukin, Ranchu, Telescopic Eye goldfish, fan-tailed goldfish, and Pearlscale goldfish.

In summary, double-tailed or fancy goldfish are much more highly bred than single-tailed types, and so are genetically further removed from the original, wild form.

Because they’ve been inbred with such pronounced mutations, fancy goldfish tend to be less robust, less hardy, slow swimmers that are less long-lived than their single-tailed relatives.

We’ll discuss the ethics of keeping them in the FAQs at the end of the article.

Introducing the Pearlscale Goldfish

Pearlscales are a breed of fancy goldfish that have round, egg-shaped bodies and pearl-like scales.

Known as ‘Chinshurin’ in Japan, pearlscales can come in almost any color and variations with or without ‘head growths’, and ‘bubble domes’.

The extremely round mutation of the pearlscale goldfish has led some people to call them ‘Ping Pong Pearlscale Goldfish’, or ‘Golfball Pearlscale Goldfish’.

Although these bizarre shapes may seem entertaining to some hobbyists, the compact shape of the pearlscale causes its spine to bend and its organs to become squashed into an unnatural shape.

Because of this, pearlscales are weak swimmers, often develop health problems like swim bladder disorder and bloating, and are less tolerant of low temperatures.

What Defines a Pearlscale Goldfish?

Pearlscale goldfish are extremely highly bred and must have the following characteristics to qualify as a true pearlscale breed:

  • Depth of body must be greater than 2/3 of body length
  • Domed scales
  • Single dorsal fin, but all other fins in pairs
  • Caudal fin divided and forked
  • Extremities of the fins slightly rounded
  • Minimum body length 2¼ inches
  • Additionally, individuals with intense colors extending into the fins are especially highly prized.

How Big Do Pearlscale Goldfish Get?

Goldfish grow quickly in their first year of life, growing up to 2.8 inches long by 12 months of age. After this, their growth rate slows down, only gaining about an inch per every additional year.

Mature fancy goldfish specimens can reach 8 inches long, but sadly, due to health problems and being kept in cramped conditions, many pearlscales don’t ever make it to full maturity.

Pearlscale Goldfish Care Guide

Tank Size

People often keep goldfish in tanks and enclosures that are far too small for them.

Since pearlscales can reach 8 inches long, they’ll need at least a 30-gallon tank to remain in good health.

Larger tanks also offer a much more stable water quality than small tanks which is an important attribute when keeping goldfish which are notoriously messy!

Tank Environment

Goldfish aren’t too fussy when it comes to their surroundings, but it’ll be a much more rewarding experience if you create an aesthetically beautiful and practical tank environment for them.

Pieces of driftwood can look attractive but remember that raw driftwood can release tannins, turning the water an amber color and more acidic.

As for substrate, gravel is your best choice for goldfish. It’s the easiest substrate to keep clean – an important asset when looking after these messy fish!

Round pieces of rock and stones can look great in a goldfish tank, but avoid rocks with rough or sharp edges since they can easily damage fancy goldfish scales and fins.

Aquatic Plants

Many people find it difficult to grow aquarium plants alongside goldfish because of their tendency to eat them or tear them out of the substrate. Because of this, some well-anchored synthetic plants may be a better option.

Vigorous floating plants like duckweed and Amazon frogbit may also grow faster than your goldfish can eat them, and perform a useful service in absorbing excessive nitrogenous waste from the water.

Water Temperature

Pearlscale Goldfish are categorized as coldwater fish, but they actually need relatively mild water to remain healthy.

The ideal temperature to keep them is between 65-72°F, so if their tank is sited in a particularly cold room, a reliable aquarium heater will help to keep the temperature within the ideal range. In a warm room, they can be kept without a heater.

Because fancy goldfish don’t do well in water temperatures below 60°F, they shouldn’t be kept in garden ponds. At the same time, the cool water preference of goldfish makes them incompatible with most tropical fish that require warmer temperatures.

It’s also important to note that, like tropical fish, Pearlscale Goldfish are sensitive to sudden changes in water temperature, so acclimatizing them properly in a new tank is essential to avoid thermal shock.

Water Parameters

Goldfish are relatively tolerant when it comes to their water chemistry. A fairly neutral pH of between 6.5-7.5 is ideal, but they’ll also tolerate water conditions of between 6-8.

Try to keep the carbonate hardness of the water above 4 dKH to guard against sudden changes in the water’s pH.


Goldfish have a huge bioload and are some of the messiest fish you can keep! Despite common myths, they must never be kept without an effective aquarium filter.

Hang-on-back filters and internal power filters are good options for small to medium-sized tanks, and canister filters are the best choice for larger tanks. However, because they are highly bred and fairly weak-swimming, fancy goldfish won’t enjoy swimming against a strong filter flow.

To reduce the water current without compromising the filter’s efficiency, I recommend using an aquarium spray bar, or lily pipe.


Like other types of goldfish, pearlscales are phenomenally greedy and will eat almost anything you throw at them! Their constant begging for food leads many owners to overfeed them, which can be fatal for 3 reasons:

  • Overfed goldfish can easily develop digestive problems, and bloat, leading to swim bladder disease.
  • Overfed goldfish will produce more digestive waste which can lead to ammonia poisoning or high nitrate levels.
  • Any uneaten food will rot and contaminate the tank water, again leading to potentially fatal conditions.

Therefore only feed your goldfish twice a day with no more food than they eat within 2 minutes.

High-quality specialized goldfish food is your best option for dried food for your goldfish. Dried fish foods, however, should always be supplemented with fresh and frozen foods such as bloodworms, tubifex worms, daphnia, brine shrimp, mysis shrimp, and mosquito larvae.

Since their ancestors ate lots of vegetable matter, goldfish will also appreciate regular helpings of organic spinach, kale, dandelion leaves, spirulina wafers, and algae wafers.

Compatible Tank Mates

As I’ve already mentioned, Pearlscale goldfish are coldwater fish, so can only be kept with other fish species that are tolerant of low water temperatures.

Other coldwater fish such as white-cloud mountain minnows and weather loaches are not suitable tank mates because they require much higher water quality than goldfish and also need highly oxygenated water with a strong current which fancy goldfish hate.

A better option is to keep fancy goldfish at the top end of their preferred temperature range and keep them with hardy fish that would normally be regarded as tropical.

Rosy barbs, gold barbs, and two-spot barbs can all tolerate water temperatures below 70°F, but may also nip at fancy goldfish fins. Zebra danios and pearl danios are more peaceful and can handle water temperatures in the mid-60s.

Buenos Aires tetra, black phantom tetra, and bloodfin tetra are also hardy species, but be sure to keep them in schools of at least 6 fish to avoid stress and the possibility of them nipping at each other or at your goldfish’s fins. Water quality also needs to be high to suit tetras.

Some algae-eating fish such as hardy cories and plecos can also be kept with goldfish under ideal conditions. Goldfish will sometimes eat aquarium shrimp and snails!

Check out my dedicated article on algae eaters and goldfish here.

Can Pearlscale Goldfish Live Alone?

Scientists often use goldfish as a subject for experiments to learn more about fish intelligence and behavior.

According to Culum Brown, a fish training expert at Macquarie University, Australia, goldfish are often used as ‘learning fishes’ because of their long memory spans and ability to learn tricks!

Although goldfish are often kept alone, I surmise that this intelligent species feels much happier when given adequate stimulation. Tankmates provide companionship for your goldfish and also add interest to your fish tank.

If you do choose to keep your goldfish alone, be sure to offer it plenty of stimulation yourself. You can spend time talking with your goldfish, teaching it tricks, and making the effort to feed it its favorite treats regularly.

Health and Disease

Pearlscale Goldfish are highly bred fish and tend to suffer more health problems than common goldfish.

Because their round shape creates a bent spine, pearlscale goldfish can’t swim as strongly as their ancestors. It’s even possible that the bent spine causes them frequent discomfort.

Additionally, their extremely round form causes their internal organs to become compacted, which can lead to all kinds of health problems, especially when combined with poor diet or overeating.

As we’ve already covered, overeating is a major cause of ill health in goldfish and can easily result in constipation, bloating, swim bladder disorders, and also ammonia poisoning.

Goldfish are also subject to most of the same common freshwater fish diseases as tropical fish. Ich, velvet, and flukes are all common parasitic diseases that can lie dormant in an aquarium for years until a weakened fish or very poor water quality offers them a chance to strike.

Similarly, bacterial and fungal infections like columnaris and water molds only tend to affect fish that are already in a vulnerable state.

Because Pearlscale goldfish are weak swimmers, they’re also vulnerable to having their fins nipped by other species of fish. Nipped fins can lead to fin rot – a bacterial infection that can later invade the rest of the body.

Sexual Dimorphism

There are a few basic ways to tell male and female goldfish apart by appearance alone:

  • Male goldfish tend to be a little thinner than females, especially around the belly area.
  • Females are often larger than males in all dimensions and get especially plump during the breeding season.
  • The pectoral fins and anal fins in goldfish are also longer and more pointed in males than in females.

Breeding Pearlscale Goldfish

Pearlscale Goldfish

Goldfish aren’t the easiest fish to breed in an aquarium but will breed more readily when exposed to similar temperature shifts that they’d experience in a mild climate outdoors.

This is because their reproductive systems rely on climatic changes during the spring and early summer to induce courtship and spawning.

Those looking to breed goldfish in a fish tank need to simulate these natural climatic shifts by gradually raising the aquarium heater’s thermostat.

You can find out more about breeding goldfish in our dedicated article here.


When well cared for, goldfish can live to a ripe old age. Single-tail goldfish have been known to live to 40 years!

Once again, fancy goldfish like Pearlscales tend to live shorter lives than common goldfish, but healthy fish can still sometimes live for between 8 and 15 years.

For them to reach their maximum lifespan, their diet, water quality, and quality of care must be of the highest order.

Tank Maintenance

  • Feed a diverse, balanced diet that includes regular additions of live or frozen foods and vegetable matter. Avoid overfeeding!
  • Install a good filter and clean it every 2-3 weeks.
  • Vacuum your substrate and make partial water changes of 15-35% every 1-2 weeks, with treated water of matching temperature.
  • Get yourself a reliable heater and thermometer. Make daily checks to ensure the temperature is within the ideal range for all of your fish.
  • Observe your fish closely every day to ensure they are in good health and interacting peacefully with each other.
  • Test your aquarium’s water at least once a month, or any time your fish seem unwell.

Buying Guide

As one of the most common fancy goldfish varieties, Pearlscale goldfish should be fairly easy to find if you shop around.

Always try to source your fish from reputable breeders and dealers, and observe them carefully for any signs of ill health, diseases, or swimming difficulties before you buy.


Are Pearlscale Goldfish Ethical To Keep?

Some people are understandably concerned about intentionally breeding fish with mutations that affect their quality of life.

While the bulbous head of the Pearlscale goldfish might not seem as extreme as Bubble Eye Goldfish or Telescope Goldfish, the unnaturally round shape of these fish can cause spinal problems, as well as problems with their internal organ dysfunction.

Nowadays more animal welfare authorities are speaking out about the ethics of keeping fancy goldfish. The Royal New Zealand Society for the Prevention of Cruelty to Animals concludes: ‘Prospective goldfish owners should avoid purchasing breeds that have deformities that impair the health and welfare of the fish.’

Please consider this point carefully before investing in a fancy goldfish. Goldfish live long lives, and they deserve to be happy ones. Single-tail varieties such as comets are renowned for being healthier, stronger swimming, and longer-lived than fancy fin varieties.

Are Pearlscale Goldfish Aggressive Fish?

While Pearlscale goldfish are not any more aggressive than any other type of goldfish, they are often smaller and weaker than long-body goldfish like comet, sarasa, and shubunkin varieties.

This means they are more likely to be intimidated or, in extreme circumstances, bullied, by these larger, stronger varieties. In most instances, however, goldfish are social and fairly peaceful fish that won’t fight with each other or other similar-sized fish.

Final Thoughts

Pearlscale goldfish are a famous variety of goldfish characterized by their extremely round bodies. This mutation could be considered a cruel deformity by some, and their long-term welfare must be weighed up before buying one.

If you’re looking for a goldfish that’s more likely to live a long and healthy life, then consider a single-fin variety such as a Common Goldfish or Comet Goldfish.

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