Ranchu Goldfish: Introduction & Care Guide

Ranchu goldfish – known as “King of Goldfish” – are a variety of fancy goldfish. They are hugely popular with enthusiasts around the world, especially in Asia.

These beautiful ornamental fish originated in China, being further hybridized in Japan in the late 1800s.

The Ranchu was created to represent Sumo wrestlers’ shape, which is why they have a big head and a very heavy body. It’s said that Ranchu goldfish represent all the good things about Japan and that they bring harmony to a home.

The Ranchu is a human-created variant, so there are no wild populations. Also known as the Buffalo-head goldfish, the Ranchu is one of a staggering 125 species of captive-bred fancy goldfish varieties.

Ranchu Goldfish are Show Business Stars!

Breeders exhibit their best Ranchus in shows. In Japan, the fish are exhibited in shallow dishes, which are said to represent the Sumu ring.

The dishes allow the viewer to get a close look at them and judge their shape from above.

In Japanese Ranchu shows, there are three to five judges. Each judge evaluates the fish and gives it a score. The fish are lifted out of the water by hand, before being put back into the show bowl. The judges even award points for the way the fish swims after being handled!

A show-quality Ranchu should have a long body, wide, well-developed head, and a tail that resembles “swallow’s wings.” There should be a wide “bracelet” with reflective scales that draw the eye at the base of the caudal peduncle.

Interestingly, as with most fancy goldfish varieties, Ranchu become paler and whiter as they age, a feature that doesn’t affect a fish’s success in the show ring.

The progeny of successful show Ranchu command a high price as breeding fish. However, breeders are extremely selective about who buys their stock, as preserving the gene pool’s purity is paramount. 

What’s in a Name?

Ranchu goldfish are split into age groups at shows.

“Tosai” is the name for a Ranchu in its first year.

On the following January 1, all Tosai, regardless of when they hatched in their first year, become known as Nisai.

The next January, Nisai become Oya.

Depending on the fish’s age, Oya are then known as young or old Oya.

Ranchu Goldfish Origins

All modern goldfish varieties are distantly related to Prussian Carp, Carassius gibelio. Bloch first described these fish in 1782. These carp are found widely distributed across Central Asia, where they live in slow-moving bodies of water, such as ponds, rivers, ditches, and lakes.

Carp were raised in captivity by many civilizations, including the Romans, as a food source. However, it was the Chinese who first began to experiment with breeding the fish to create ornamental hybrids that were kept purely as exotic, decorative status symbols.

In the 1500s, Chinese breeders began trading their goldfish with Japan, and the hobby caught on.

They were exported to Europe in the 1600s and to the US a couple of centuries later.

What do Ranchu Goldfish Look Like?

Ranchu are a typical egg-shaped fancy goldfish variety. Although show-quality Ranchu are longer in the body than pet specimens, the fish’s body is typically short and stubby.

The fish do not have dorsal fins and develop a fleshy “wen” on their heads. In extreme cases, that raspberry-like growth covers the fish’s eyes or nostrils, and some owners choose to have the wen surgically reduced as a welfare issue. The fish’s head is characteristically broad and larger than that of other fancy goldfish types.

A broad, highly curved back and splayed tail fin are the most distinctive features of the Ranchu goldfish. In some cases, the tail has three or four separate, distinctly rounded lobes and is tucked in at an angle of around 45 degrees. The caudal peduncle should curve down markedly to meet the tail fin.

Ranchu fancy goldfish typically grow to measure around 5  to six inches long, although larger specimens have been reported.

When given the correct care and a nutritious diet, Ranchu goldfish usually live for ten to 15 years. Though a lifespan of 20 years plus is not uncommon.

Ranchu come in a variety of colors, including:


  • White/red
  • Calico (Edonishiki)
  • Black
  • White
  • Deep red
  • Yellow-orange shaded
  • Red with white-edged scales

The Ranchu’s scales can be metallic or matte.

Is the Ranchu Goldfish Suitable for Beginners?

Unlike flat-bodied varieties of goldfish, the Ranchu is rather delicate and does not tolerate poor water quality.

Although relatively hardy like most goldfish, the Ranchu’s clumsy swimming style means that it needs plenty of swimming space and doesn’t thrive when kept with faster tank mates who would outcompete the slow-swimming Ranchu for food.

Ranchu are often highly inbred, which creates genetically weak specimens and makes the variety liable to suffer from inherited health problems. Also, the wen can be prone to infection or damage, too.

The Ranchu is therefore best-suited to experienced aquarists.

Ranchu Goldfish Care Guide

If you have experience in keeping fancy goldfish and you want to be the proud owner of a beautiful, enigmatic Ranchu, here’s everything you need to know about their care.

Tank Size

Ranchu need a spacious tank where they can swim around without the risk of bumping into things. That’s especially important as the fish mature, and the wen grows larger.

These are quite large fish, so you need to provide a tank of at least 10 gallons for one Ranchu, although we recommend that you begin with a 20-gallon or 30-gallon tank if you have the space for one in your home.

Allow a further 10 gallons per additional Ranchu or other fancy goldfish that you add to your aquarium. Don’t overcrowd the tank! Overcrowding leads to poor water quality and will also stress the fish, potentially causing health problems.

What Shape Aquarium Should I Choose?

Goldfish need well-oxygenated water. For that reason, we recommend that you choose a long tank that has plenty of surface area. That will enable better gaseous exchange than a tall tank or bowl.

Ranchu swim in all areas of the tank, spending lots of time rooting around in the substrate for scraps of food, as well as enjoying a swim in open water. We find that a long, rectangular tank best accommodates both of those requirements.

Does My Ranchu Goldfish Need a Filter?

Absolutely, yes!

Goldfish are large, very dirty fish, and they produce a lot of waste.

If you observe your Ranchus, you’ll notice that they spend much of their time foraging for food. Unlike humans, goldfish don’t have a stomach, so whatever they eat passes straight through the fish’s gastrointestinal tract and into the water.

A powerful filtration system is essential for a goldfish tank. The mechanical filter should circulate the water at a GPH (gallons per hour) rate of at least four times the volume of the tank. So, if you have a 30-gallon tank, your filter should have a GPH rate of at least 120.

As these fish are poor swimmers, make sure that the plants or décor buffer the water flow. This will help the Ranchu to move around their tank more easily.

Water Parameters

Ranchu are coldwater fish that prefer a temperature of between 65o and 72o Fahrenheit. Unlike flat-bodied goldfish types, Ranchu cannot tolerate temperatures below 60o Fahrenheit.

The pH range should be between 6.0 to 8.0, with a water hardness of 5 to 19 dGH.

Tank Décor

Whatever decorations you choose for your tank, ensure that there are no sharp edges or points that could injure the Ranchu’s vulnerable wen. Smooth, medium gauge gravel works well as a substrate, and flat rocks and pieces of driftwood can give the aquarium a natural look.

Aquatic plants make an attractive, safe addition to the tank. Living plants can also help to oxygenate the water and remove harmful nitrates, which the plants use as a source of nutrition. However, unfortunately, Ranchu will eat tender leaves and dig up roots, too, if you don’t anchor the plants securely in the substrate. 


If you have living plants, you will need lighting for your aquarium. Although Ranchu don’t need lights, a good quality LED lighting unit will display your fish’s colors beautifully.

Diet and Nutrition

Like all goldfish varieties, the Ranchu is an omnivore, eating a diet that includes plant matter and meaty protein.

Egg-shaped goldfish often suffer from digestive problems, such as bloat, Swim Bladder Disease, and constipation, often caused by a diet containing too much dried food.

You can help to prevent those digestive issues by feeding your Ranchu a diet that includes plenty of frozen or fresh bloodworms, daphnia, tubifex worms, and brine shrimp. Choose goldfish flakes or pellets that are formulated specifically for fancy, round-bodied goldfish.

Is it Safe to Feed Live Food to Ranchu Goldfish?

Ranchu enjoy live food in their diet, but you must be careful where you source it, as live food can sometimes contain parasites or bacteria that could infect your fish.

If you decide to offer your fish live bloodworm or daphnia, use a reputable supplier, and always remove the food from the water it comes in before putting the food into your tank.

Never take live food from the wild environment!

The safest way to provide your fish with live food is to raise brine shrimp at home if you have space and time to devote to that.

How Often Should I Feed My Ranchu?

Adult Ranchu should be fed two or three times a day. Juveniles and Ranchu being prepared for the show ring can be fed up to six times a day. If you’re not around during the daytime to feed your fish, it’s worth investing in a high-quality automatic fish feeder to do the job for you.

Offer your fish enough food to keep them busy for a couple of minutes at each feed so that you don’t overfeed them. However, fish with very large wens will need extra time to feed, as their vision is often poor.

Tank Mates for Your Ranchu

Ranchu are highly social creatures that do best when kept in a group of other similar fancy goldfish types, such as Lionhead, Celestial, Bubble-eye, or Telescope goldfish.

Avoid keeping Ranchu with fast swimmers that would outcompete the slower fancy goldfish for food.

It’s also not recommended that you keep large Ranchu with very tiny nano fish that would be viewed as a snack! Shrimp are also unsuitable companions for fancy goldfish for the same reason. However, a few large snails can make useful additions to the tank, as they help keep algae down.

Breeding Ranchu Goldfish

Ranchu goldfish are egg-layers that will readily spawn if provided with the right conditions.

You can breed Ranchu in groups of five or more. In outdoor conditions, goldfish spawn in the spring when the water warms. So, you can encourage spawning in the captive environment by replicating that.

Sexual Differences

It is very difficult to tell whether goldfish are male or female. However, males are typically slimmer and smaller than females, and they develop white “prickles” called breeding tubercles on their gill covers when in breeding condition.

Spawning Tank

Use an aquarium of at least 20 gallons as a spawning tank.

Provide plenty of lush planting, spawning mats, and some solid surfaces to which the eggs can stick.

Encouraging Spawning

Ensure that your breeding stock is healthy and free from disease. Feed the fish plenty of good quality live food in the two weeks before you attempt to induce spawning.

Some breeders separate their male and female fish for three weeks or so before breeding to increase their interest in spawning. Introduce the male and female fish to the spawning tank at the same time.

Gradually reduce the temperature in the tank to around 60o Fahrenheit, and then warm it by 3o Fahrenheit every day until the Ranchu begin spawning.

Keep the environment scrupulously clean by carrying out 20% water changes every day and removing uneaten food from the substrate with an aquarium vacuum.

Spawning and Raising Fry

When the fish are ready to breed, their colors will intensify, and the male will pursue the female around the tank, pushing against her until she drops her eggs. The male Ranchu then fertilizes the eggs.

Unfortunately, goldfish tend to eat their eggs, so you’ll need to remove the parents from the tank once the eggs are laid.

The eggs usually hatch within four to seven days. Feed the fry on specialty fry food until they’re big enough to cope with crushed flakes or baby brine shrimp.

Health and Diseases

Ranchu are moderately hardy fish, but they can be vulnerable to the same diseases as most captive fish species. The best way to prevent outbreaks of disease is to keep your aquarium clean and provide your fish with a high-quality, varied diet.

Fortunately, if caught early, all the following conditions can be treated successfully. You’ll just need an appropriate over-the-counter medication you can buy from a fish or pet store.

Protozoan Parasites

Ranchu goldfish can be affected by several diseases, all of which are caused by various aquatic protozoan parasites.

Ich is often seen in aquarium fish and is commonly known as White Spot Disease. Ich manifests as a sprinkling of tiny white spots across the fish’s gills, fins, and body.

Chilodonella and Costia are also caused by protozoan parasites. These parasites cause cloudiness of the fish’s skin.


New fish, plants and live food can all introduce parasites to your tank.

Flukes, fish lice (argulus), and anchor worms can sometimes be seen by the naked eye, fixed to the fish’s body or gills.

Fungal Infections

Fungus appears as cotton-like growths on the affected fish’s mouth, gills, or body. There are many different species of fungus that can affect aquarium fish, all of which are easy to treat.

Bacterial Infection

All fish tanks contain bacteria. However, your fish will only be affected if injury or stress has weakened them.

A Ranchu with ulcers, sores, or red patches on its fins or body is most likely being attacked by bacteria.

Bacteria also cause Fin Rot, which is a condition where the fish’s fins become ragged and torn.

Swim Bladder Disease

All round-bodied varieties of fancy goldfish are vulnerable to Swim Bladder Disease.

The fish’s swim bladder is an organ that enables the fish to remain stable and upright in the water. Fish with Swim Bladder Disease are unable to remain on an even keel, floating to the surface, sinking to the bottom of the tank, or becoming stuck on one side.

Poor water quality and dietary issues are the usual causes of swim bladder problems. You can often remedy the issue by starving the fish for 24 hours and then offering thawed frozen food, live blood worms, or a defrosted pea with the skin removed.

Are Ranchu Goldfish Readily Available?

Yes! Many fish stores and websites sell Ranchu goldfish.

Young fish are usually priced around $10 to $15.

However, if you want a high-grade specimen that has very good bloodlines or is an unusual or particularly desirable color, such as calico, you can expect to pay $100 or even more.

In Summary

Ranchu fancy goldfish are unusual and attractive fish that can make excellent, long-lived pets for fish keepers who have experience in caring for these delicate creatures.

For a Ranchu to remain healthy and thriving, you’ll need to provide him with a large tank, company of his own kind or similar, a well-balanced, high-quality diet, and clean, well-oxygenated water.

It’s also possible to raise Ranchu in your home tank, maybe with a view to exhibiting them in shows.

Tell us about your Ranchu in the comments box below, and please share this article if you enjoyed it!

1 thought on “Ranchu Goldfish: Introduction & Care Guide”

  1. Among all my 36 Goldfishes consist of almost different breeds my only my Ranchu had their eyes dropped. I have 6 Ranchu of which 5 of them had their eyes missing from 1 eye each to 2 eyes after about 2 weeks later.

    Though they had dropped both of their eyes but they are still very healthy they eat well & swim well.
    Now I separated all my 6 Ranchu with others Goldfishes in a separate tank.

    Anticipating for your professional advices on this eyes missing problem.


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