Watonai Goldfish: Care Guide, Lifespan and More

Most goldfish are pretty easy to care for, enjoy a long lifespan, can live happily in a garden pond and make beautiful pets. For that reason, goldfish remain just about the most popular pet fish species on the planet! 

But, if you’re an experienced goldfish keeper with some spare cash to splash on a rare fish, you might want to consider adding the Watonai goldfish to your collection.

Watonai goldfish are a seldom-seen variety of flat-bodied goldfish – read our guide to learn how to care for these rare and beautiful coldwater fish.

Origins of the Watonai Goldfish

Every goldfish is distantly related to a species of common Prussian carp. As early as the 1700s, the Chinese were raising these fish in ponds for food. 

Sometimes, the carp produced a few brightly colored individuals among the regular drab silver and gray fish. The fish keepers kept those “goldfish” as ornamental pets.

It was eventually discovered that more colors and forms of the carp could be created by crossbreeding the fish. The hobby caught on, and by the 1800s and early 1900s, goldfish were regularly being traded as a valuable commodity throughout Asia, Europe, and eventually, the US. 

These days, there are over 200 different types of goldfish, all dating back to those tasty early carp! 

But you won’t see a school of goldfish swimming in a pond or lake in the park since every goldfish is captive-bred. However, goldfish can grow to a pretty large size, and sometimes owners release their pets into the wild when their home tank is outgrown. 

Unfortunately, these rogue goldfish don’t tend to last long in the natural environment, as their bright colors quickly attract predators from both the air and the water.

What is a Watonai Goldfish?

The Watonai goldfish is an extremely rare variety of Fancy Goldfish.

These fish were first described in 1908 by Dr. Sinnosuke Matsubara. It’s thought that the fish were bred in Japan, being created from a cross between a fantail Wakin and a humpbacked Ryukin.

The early Watonais had an extravagant, long double tail and hardy, cold-tolerant constitution. Sadly, the ribbon-tailed variety of these fish vanished by the middle of the century and is thought to have gone extinct. 

Some breeders have tried to recreate the variety by introducing new lines from fresh Wakin/Ryukin crosses. 

Watonai goldfish have a long, streamlined body with a dorsal fin. The fins fan out behind the fish as it swims, and the gorgeous double ribbon tails are typically as long as the fish’s body.

Do you keep Watonai goldfish? Let us know in the comments box below!

Watonai Goldfish Lifespan

All goldfish generally enjoy a long lifespan, and the Watonai is no exception, often surviving for over 15 years if provided with optimum living conditions and a high-quality, balanced diet.

What Size are Watonai Goldfish?

Juvenile Watonai goldfish measure an inch or so in length. Adults can grow to an average length of ten to 12 inches when fully mature, and you must bear that in mind when choosing a tank for your fish.

Pond-kept Watonai can attain a spectacular 19 inches in length, plus their tail!

Colors and Patterns of the Watonai Goldfish

Watonai goldfish come in an impressive array of colors and patterns, including:

  • Red
  • White
  • Orange
  • Blue
  • Yellow
  • Black

As well as solid colors, the fish can be bicolored or tricolored. These beautiful creatures can also be Sarasa, which is a combo of multiple colors, generally including blue.

Price and Availability of Watonai Goldfish

Watonai goldfish are extremely rare and valuable, often costing in excess of a few hundred pounds/dollars each for high quality specimens! 

You won’t find these fish in your high street pet store, but you can sometimes get them online through specialist breeders and dealers.

Are Watonai Goldfish Suitable for Beginners?

Although the Watonai is a hardy fish that can do equally well in a pond or aquarium setting, we don’t recommend them to beginners simply because of the price of these seldom-seen fish.

Watonai Goldfish Care Guide

If you decide to take the plunge and invest in a Watonai goldfish, you can learn how to care for these rare creatures in the next part of our guide.

Watonai Goldfish Tank Size

For a single Watonai, you’ll need a 30-gallon tank. All goldfish do best when kept in groups, and you’ll need an additional 15 to 20 gallons per fish to provide enough space for your fish. 

Tank Shape

To give the fish plenty of swimming space, we recommend a long, wide tank.

Watonai are good swimmers, and they are perfectly capable of jumping right out of their tank if startled. For that reason, you need a tank with a cover slide or a tightly fitting lid. 

A cover is a good idea for any fish tank, as that can prevent evaporation and keep dirt and dust from contaminating the water.

Do not keep goldfish in a bowl! Goldfish bowls do not provide sufficient swimming space or dissolved oxygen for goldfish.

How many Watonai Goldfish can you keep?

Generally, you should allow 1 gallon of water per 1 inch of fish. However, the larger the aquarium you can provide, the better it is for your fish. Watonai goldfish are peaceable, friendly fish that enjoy the company of others of their kind. 

Since this goldfish variety are strong swimmers, these curious fish need lots of space to explore and swim around their environment. 

If denied that swimming space, the fish will get stressed, leaving them at risk of disease. 

Goldfish are greedy feeders, and the jostling that occurs at mealtimes can often result in injuries if the tank is overcrowded.

Water Parameters

Temp (oF)pHHardnessAmmoniaNitrate
60o – 78o F6.0 – 8.05 – 19 dGH0>20ppm
Water parameters for a Watonai Goldfish

Watonai goldfish can live in cooler water conditions than many Fancy Goldfish. As long as the water is within the range of 60o and 78o Fahrenheit, the fish will be happy. The water pH should be in the range of 6.0 to 8.0, with a water hardness of between 5 and 19 dGH.

Ammonia and nitrite levels in the tank must always be zero, with nitrate levels of less than 20ppm. However, it’s worth noting that tap water often contains nitrate levels of up to 20ppm, so your Watonai should do fine as long as the nitrate levels are lower than 30ppm.


Goldfish continually produce waste as they swim around the tank. That means you’ll need a highly efficient, powerful filter unit that circulates the total volume of water through your tank at least four times every hour.

Although the Watonai is a relatively strong swimmer when compared to the round-bodied goldfish varieties, a strong current can present problems for the fish because of its flamboyant tail finnage. 

So, we recommend that you use a filter system with an adjustable outflow valve to divert the flow away from the fish’s swimming area. Alternatively, use decorations or plants to baffle the current.

Tank Maintenance

You’ll need to keep on top of aquarium maintenance to keep the tank environment healthy and safe for the goldfish.

Perform 30% water changes every week to remove nitrates from the aquarium. You also need to use an aquarium vacuum cleaner to remove all solid organic waste from the bottom of the tank, in the substrate, and around plants and decorations.

Snip off dead plant leaves and stems, and remove patches of unsightly algae from the viewing panes with an algae scraper.

Tank Decoration

When choosing decorations for your aquarium, you can pretty much use whatever takes your fancy. However, there are a few important considerations to bear in mind.

How do you decorate your goldfish tank? Tell us in the comments box below!

Safety First

Watonais have beautiful trailing tails that can present a hazard to the fish because those glorious fins can get snagged and torn on rough or sharp objects. So, stick to using smooth pebbles, flat stones and driftwood when decorating your tank.

Keep your decorations and planting to the perimeter of the tank so that there’s plenty of open swimming space for the fish.

The best substrate to use is large-gauge, smooth gravel that won’t damage the fish’s fins while the Watonai is foraging through the substrate for scraps.

What about Plants?

Living plants are beneficial for every fish tank. Plants add beauty and ambiance to the aquarium while removing nitrates and CO2 from the environment and adding valuable oxygen.

Unfortunately, goldfish are inclined to nibble on plants, and the fish’s habit of rooting through the gravel for food scraps can uproot plant stems. 

Try using plants such as Anubias, Java fern, and Marimo Moss Balls that are not appetizing to the goldfish and are not easily uprooted.

If you don’t want the hassle of keeping living plants, you could consider using silk ones instead. Silk plants can look beautiful, and they’re easily replanted if the fish dig them up. However, plastic plants are not a good choice, as they often have sharp points that can easily damage your Watonai.


If you keep living plants, you’ll need at least eight to ten hours of light per day in your aquarium.

Your fish will appreciate the light, too, as a clear daylight and night cycle tells fish living in an artificial environment when to feed and become active and when to rest. 

If the fish are deprived of that natural cycle, they become stressed, which leads to a compromised immune system and potential health problems.

If you don’t have a lighting system with an auto-timer function, try using a cheap DIY store timer plug instead.

Nutrition and Feeding

Goldfish are omnivorous fish that need a varied diet of meaty protein, algae and some plant matter.

In captivity, you can feed your fish a diet of high-quality goldfish flakes or pellets. Your fish will also need some frozen meaty foods, and they’ll enjoy a few fresh veggies, including zucchini and spinach.

Watonai goldfish enjoy grazing on green algae throughout the day, so you might want to leave a small patch of algae somewhere discreet that your fish can enjoy between feeds.

What about Live Foods?

If you keep your Watonai goldfish in a pond, they will take insects, worms, larvae and crustaceans that live in the environment.

You can buy live fish foods from pet stores, but we don’t recommend them. All too often, live foods come with an unwanted cargo of parasites that could put your rare Watonai in danger.

Instead, give your fish frozen meaty foods or invest in a home brine shrimp hatchery.

How Much Should You Feed Watonai Goldfish?

Watonai goldfish should receive two or three small meals every day.

Give your goldfish only what they will finish up in a few minutes so that you don’t overfeed them.

What are Good Tank Mates for Watonai Goldfish?

Watonai goldfish are peaceful fish that do best when kept with other goldfish. You can create a harmonious community of different kinds of goldfish in the same pond or tank. 

However, we recommend that you don’t include the slower-moving varieties of round-bodied Fancies with faster swimming types. 

Slim-bodied goldfish typically stress the slower swimmers by outcompeting them at feeding times and buffeting them as they dart around the aquarium.

Large varieties of freshwater shrimp and snails can make a useful, interesting cleaning crew. However, you must ensure that these creatures are not small enough to be viewed as a food source by your goldfish!

Do you keep Watonai goldfish with other types of goldfish? Leave a comment!

Health and Diseases

Although they might look delicate, Watonai goldfish are hardy creatures. That said, some common fish diseases can affect your fish.


Ich or Ick is also commonly referred to as White Spot Disease.

Fish with Ich are usually seen flicking their bodies against plants and other objects in the tank in an attempt to dislodge the Ich parasite from their skin. After a few days, a rash of white spots appears over the body, gills and fins of the affected fish. 

Fortunately, Ich is pretty easy to treat with an over-the-counter medication that you’ll get from your local pet store.

Bacterial Infections

Bacterial infections can affect fish living in both fish tanks and ponds. There are lots of different kinds of bacteria that attack goldfish, presenting with lots of symptoms, including:

  • Skin ulcers
  • Lethargy
  • Ripped fins
  • Lost scales
  • Poor appetite
  • Breathing problems

Most minor bacterial infections can be dealt with using a broad-spectrum antibacterial drug that you’ll get from your vet or pet store.


Flukes are external parasites that can attack goldfish. Different species of flukes include:

  • Anchor worms
  • Fish lice
  • Skin flukes

Flukes typically find their way onto your fish via new fish, attached to plants, and with live food. 

The best way to prevent flukes from getting into your aquarium is by quarantining new additions for a couple of weeks. 

You can also treat the quarantine tank with an antiparasitic medication.

Breeding Watonai Goldfish

Since Watonai goldfish are so rare, breeding them in a home tank is not recommended.

These fish are a hybrid variety that’s created by mating two specific goldfish types. 

To maintain the characteristics of the Watonai goldfish it’s critical that you preserve the breed. That’s not easy for an amateur breeder to achieve, so breeding these fish is probably best left to a professional.

That said, if you exclusively keep Watonai goldfish and they live in a pond, it’s likely that you’ll end up with broods of fry during the spring months when the weather warms up. 

Provided you started with correctly bred Watonais, the offspring they produce should also be pure, genuine Watonai goldfish.

Final Thoughts

Watonai goldfish are one of the rarest goldfish you can find. Although these fish are easy to care for and pretty hardy, they are very expensive to buy. For that reason, we don’t recommend them for beginners.

You can keep Watonai goldfish with other similar types of goldfish in an outdoor pond or large aquarium. 

The fish are omnivores, eating a diet of plants, algae and meaty protein. Keep your fish’s tank or pond clean and free from nitrates, offer the Watonai a high-quality diet, and you can enjoy them for 15 years or even longer.

Do you keep Watonai goldfish? Did your fish breed naturally in your pond? Tell us about your rare goldfish in the comments box below.

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