Care, Tank Size, Lifespan, Setup & More



Ranchu goldfish are strange but cute looking fish that appeal to a large number of aquarists. Because of their unique appearance and the entertaining behavior they exhibit, they will continue to be one of the most popular goldfish varieties for quite some time!

This guide will teach you everything you need to know about Ranchu goldfish care. We dive into tank size, lifespan, food, tank setup, size, and more!

Species Summary

The Ranchu goldfish is considered the “king of all goldfish” by many. When you see one, it’s not hard to see why. This species is unique, beautiful, and undoubtedly regal.

This fish belongs to a group known as “fancy goldfish.” Fancy goldfish are specifically bred to have distinct, attractive traits. You won’t find any in the wild. These beauties are a product of centuries of selective breeding.

Ranchu goldfish in a large home aquarium tank

The unique thing about the Ranchu goldfish is that it didn’t originate in China like most Fancies. The earliest record of the Ranchu is from the 1600s in Japan. If you know anything about breeding processes and the many variants of goldfish, you can notice little quirks about the Ranchu that scream “Japan!”

They didn’t come to China until hundreds of years later when the fish-keeping hobby was more widespread. Not long after that, they went worldwide. Today, Ranchu goldfish are sought-after by collectors and aquarists around the world.


If you’re looking for a popular type of goldfish with a slew of unique quirks, the Ranchu may be for you. They’re unlike most tropical fish species. While they were likely created from wild carp, they don’t look anything like fish you’ll find living in nature.

Let’s start with the profile. The Ranchu goldfish has a bulbous, egg-like body. On the top of the body, you’ll notice a distinct curve. These freshwater fish have no dorsal fin, making that curve stand out.

The tailfin is unique, too. The base of the tail tucks inward, giving the fish a distinct “hunchback” posture. Ranchu goldfish have an expansive double-fan tail, creating a stunning burst of plumage.

The head features a fleshy growth called a helmet. It’s similar to the wen you see on lionhead goldfish and other species. However, the helmet covers more of the fish, acting like a hat over the top of the head, gills, and cheek. This growth has a similar texture to a raspberry.

Author Note: Every fish is unique, and the helmet size can vary dramatically. For some, it’s pretty subtle and blends in with the fish’s color. For others, it stands out and grows so much that it affects visibility!

Ranchu goldfish come in many colors. You can find a specimen with the iconic shimmering gold color. However, there are also white, black, and calico-style specimens.

Ranchu Goldfish Lifespan

The average Ranchu goldfish lifespan is between eight and 15 years.

Like all fish you keep in captivity, a Ranchu’s lifespan is not guaranteed. Many factors come into play, and the quality of care you provide makes a big difference. These freshwater fish have limited genetic diversity, making them susceptible to a wide range of conditions.

If they live in a poorly maintained tank or don’t receive a nutritionally balanced diet, it’s entirely possible that they won’t even reach the low end of this range.

Average Size

There’s a good amount of size variation when it comes to this fish. The typical size of a Ranchu goldfish will reach five to eight inches in length when fully-grown.

Author Note: If they live in a particularly large tank, Ranchus can get much bigger. They’re known to grow to nearly a foot long, and those inhabiting outdoor ponds with hundreds of gallons of space can reach lengths of almost 18 inches! It all depends on their habitat.

Ranchu Goldfish Care

Ranchu goldfish care can be a rewarding experience. This species is revered among collectors, and you often see excited aquarists showing off their fish at shows.

They’re not the most challenging fish to take care of, but Ranchu goldfish have unique care requirements you must meet if you want them to thrive. Their history of selective breeding also opens the doors for possible health issues, making high-quality husbandry a must.

Follow these guidelines, and you should have no problem keeping your fish happy and healthy.

Tank Size

Ranchu goldfish don’t have massive tank size requirements. They’re not the most powerful swimmers, either, eliminating the need for a huge tank that can support fast swimming.

You can technically keep a younger juvenile in a standard 10-gallon tank, but to support the health and well-being of an adult you’ll need at least 30 gallons. However, many experienced aquarists won’t go with a tank size smaller than 55 gallons for a single Ranchu if they have the space.

More space is always welcome. Despite their laid-back lifestyles, a tank that’s too small can present many problems. In small living spaces, you stunt the fish’s growth, preventing it from reaching its full size potential. Plus, cramped quarters present a never-ending source of stress and potential disease.

Author Note: As a rule of thumb, add about five gallons of volume per fish you want to add. You can even consider keeping Ranchus in a pond if you live somewhere with a temperate climate.

Water Parameters

Ranchu goldfish don’t live in the wild, but their genetic ancestors did. The best thing you can do to create a comfortable environment is to mimic the cooler streams of Asia, where wild carp reside.

This species prefers relatively cool waters with a reasonably neutral pH balance. They’re not keen on fast-moving currents, but they do love oxygenation.

When establishing and maintaining an aquarium, the most important thing is to focus on stability. Once you get the correct parameters, monitor the tank regularly to avoid significant fluctuations.

  • Water temperature: 65 to 75 degrees Fahrenheit
  • pH levels: 7.0 to 8.0 (Aim for neutral)
  • Water hardness: 5 to 19 DH

Tank Setup

Creating a natural and enriching environment is an important part of Ranchu goldfish care. However, it’s worth pointing out that this species is quite adaptable.

The most important thing to remember is their delicate nature. Avoid anything sharp or jagged that could harm the fish’s fins or body. Beyond that, you have free rein to create a pond-like tank setup.

An adult Ranchu goldfish

Start with a layer of sand or smooth pebbles. Ranchu goldfish have a penchant for digging around and moving substrate, so don’t be surprised if hills and pits form.

Generally, plants aren’t a good idea for Ranchu goldfish. They tend to uproot flimsier plant cultivars and feed on their leaves. However, you can try plant species like anubias, java fern, and java moss. Anchoring them to sturdier rocks avoids the uprooting issue.

Next to decor, equip your tank with an appropriately sized filtration system. Ranchu goldfish can produce a significant amount of waste, and you need a filter to handle it.

Author Note: Avoid creating strong currents with outlets or pumps. Air stones are beneficial, but traditional pumps can create too strong of a flow that these weak swimmers can’t overcome.

Common Possible Diseases

Unfortunately, the Ranchu goldfish is often considered a sensitive freshwater fish. This can be influenced a bit based on the genetic diversity of each specimen, but most Ranchus have moderate to high disease risks.

The good news is that you can avoid problems by keeping your tank well-maintained. Continually monitoring conditions and weekly water changes to keep ammonia levels low goes a long way.

The most common diseases you have to be wary of with the Ranchu goldfish are Ich, velvet disease, and fin rot.

If you have any experience with fish-keeping, you probably know about Ich. It’s a stress-related condition that occurs when the water parameters sour. The fish become stressed out, allowing protozoan parasites to take hold.

Ich is a contagious disease that causes white spots to form all over the body. It can be lethal, but it’s also easy to treat.

Velvet disease can also occur due to stress. With this malady, a tiny parasite called oodinium attacks the fins, gills, and body. It creates rust-colored patches to form. It may also cover the fish in a velvet-like film.

Finally, we have fin rot. As the name implies, this condition often affects the fins. In the case of the Ranchu goldfish, that gorgeous double-fan fin is the target.

Fit Rot is a bacterial disease that eats away at delicate fin tissue. It can pave the way for more dangerous infections to occur and affect the fish’s ability to swim.

Food & Diet

Ranchu goldfish always seem to have a healthy appetite! They’re omnivores that will consume both plant and protein-based foods.

The best diet usually consists of nutritionally balanced flakes or pellets. There’s no shortage of high-quality formulas on the market today, and many will help bring out your goldfish’s color.

Many owners will also supplement commercial food with high-protein snacks. Ranchu goldfish love insects, tubifex, bloodworms, and other similar foods. They’ll gladly accept live, frozen, or freeze-dried foods, but most aquarists avoid live foods due to the fish’s lackluster swimming abilities.

Author Note: Ranchu goldfish need to eat two or three times a day. During those feedings, provide enough food that your fish can eat in two minutes. Anything more than that, and you run the risk of overfeeding them. That could lead to health problems and changes in the water chemistry.

Behavior & Temperament

This species of fancy goldfish is calm, easy-going, and pretty fun to watch.

As mentioned earlier, they’re not speedy swimmers. Their anatomy prevents them from zipping back and forth across the tank. But they make due and will explore the environment just like any other fish.

They bob along the water and have a unique swimming style. They move their tails back and forth, allowing that flowing tissue to dance with movement.

Throughout the day, your fish will likely explore any decor you have. They may try to uproot plants and nibble on leaves, but their behavior is relatively calm by comparison.

Author Note: Aggression is virtually non-existent with Ranchu goldfish. They’re peaceful fish that do very well as a community fish.

Tank Mates

Ranchu goldfish are perfect for multi-species tanks, but you must be mindful of how others might affect the fish’s well-being. They’re not aggressive, but they will be the target of fish species that are!

Avoid larger bullies like Cichlids and Oscar Fish. Even smaller fin-nippers are out of the question because they love to take advantage of the Ranchu’s flowing tailfin.

The best Ranchu goldfish tank mates are cold-water species with the same peace-loving temperament. Good options include:


The most challenging part of breeding Ranchu goldfish is sexing. Males and females look almost identical. However, males will develop tubercles on their gill plates and faces at maturity.

Most breeders will attempt to breed a group of fish, allowing them to pair off naturally.

Once you find suitable pairs, set up a sizable breeding tank. Conditions can be identical to the main tank, but you want to fill the space with fine-leaf plants. You can also use grasses, breeding nets, and other accessories to protect the eggs.

Females will potentially lay thousands of eggs during a single spawning session. This species is an egg-scatterer, so the mother will swim around the tank as she releases the eggs. The eggs are sticky and will attach to plants and fibers.

After spawning, remove the adults. They have no parental instincts and will likely try to eat the eggs.

Eggs hatch in two to three days. The fry then absorbs their egg sac for another few days before they are free-swimming. It’s best to keep the baby fish separate from the adults. Otherwise, they become fish food!

Allow the fish to develop in a large tank or pond. As they grow, you can provide powdered or liquid fry food before moving onto high-protein meals like baby brine shrimp or infusoria.

This species experiences fast growth during the first few months. However, their growth rate slows to about an inch a year thereafter.            

Wrapping Up

Ranchu goldfish care isn’t particularly complicated, but it’s important to get it right. These fish are quite sensitive, and won’t be able to tolerate many mistakes on your part!

If you have questions about these fish that we didn’t address in the guide above, send them over. We’ll help you out however we can.


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