Ranchu

Identification

A ranchu is recognised first by what is missing. There is no dorsal fin, and the back runs from the top of the head in one smooth, unbroken arch that drops steeply at the tail. That final drop is part of the ranchu’s look, though what the standard asks for is a short double tail set at about 45 degrees to the peduncle and spread wide, so that from above it reads as a fan. The body is short and deep, and from above the outline should be broad and roughly rectangular, with a square head and a thick back of near-even width.

The head carries a wen, the raspberry-textured growth also seen on orandas, but on a ranchu it tends to be neater and more compact, covering the head and cheeks without swallowing the eyes. Wen care covers what the tissue is and why water quality is nearly the whole of looking after it. Separating a ranchu from a lionhead is a matter of profile: the lionhead’s back is flatter and longer, its tail set shallower, its wen larger and looser. Colours include red, orange, red-and-white, white, black and calico, with nacreous red-and-white fish sold as sakura.

Oranda, lionhead or ranchu?

• 

  Oranda

  A dorsal fin

• 

  Lionhead

  No dorsal, a straighter back

• 

  Ranchu

  No dorsal, an arched back

Three hooded goldfish side by side: an oranda with a dorsal fin ringed on its back, a lionhead with its fairly straight, finless back ringed, and a ranchu with its arched, finless back ringed.

1. Oranda. The one of the three with a dorsal fin. Its hood can spread down the cheeks and over the gill covers.
2. Lionhead. No dorsal fin, and a back that runs fairly straight or gently curved, with only a mild tuck at the tail. Shops often sell it as a ranchu.
3. Ranchu. No dorsal fin, and one smooth arch from head to a tail tucked in at about 45 degrees.

Photographs: Oranda, Vassil, CC0; Lionhead, Lawrencekhoo, CC BY-SA 4.0; Ranchu, Lerdsuwa, CC BY-SA 4.0. Rings added.

The varieties, and the two traditions

The names on a shop tank describe colour; the thing that actually differs is which country’s standard the fish was bred to.

• Japanese ranchu. Bred and judged from above, in shallow tubs. Japan has two show lines judged to different standards: the Association line prizes body, tail and swimming, the Uno line wen and colour. Broad square head, thick back of near-even width, flat tail spread, compact wen.
• Chinese and Thai lines. Common in Western shops. Often selected with the side view in mind, which the side-view standard describes as shorter, deeper bodies and heavier wens. Not worse fish; different fish.
• Sakura. Nacreous red-and-white, so the scales are part translucent and the pattern has a softer edge.
• Calico and black. Black ranchus commonly lighten toward bronze with age, which is ordinary rather than a fault — pale or faded colour covers why.
• Edonishiki. A calico ranchu line.
• Osaka ranchu. A round-bodied form without a head wen, recorded in the Edo period, lost in the Second World War and rebuilt from other stocks, among them ranchu crossed with hanafusa, Izumo nankin and tosakin. Rare.

What this means practically: a “ranchu” bought in a general aquatic shop and a ranchu bought from a specialist are often quite different animals, and the price gap reflects the lineage rather than the fish’s health. Either will live happily in the same tank.

How it develops

A ranchu is judged on things that arrive at different times, which is why breeders grade the same spawn repeatedly. The wen shows from about four months and keeps filling for a year or more, while the back and tail set are judged early, because breeders say they do not improve with age. No published source gives a finer timetable.

The back and the tail set are the parts that cannot be improved later. A fish whose back runs flat into the tail may not develop the drop, whatever it is fed — which is the whole argument for buying from someone who grades, made in breeding goldfish.

And buy the tank for the adult. How big do goldfish get covers the gap between a shop fish and a grown one.

Choosing one

Look down at it before you look through the glass. That is not an affectation; it is the view the breed exists for.

1. From above: a broad, square head, a thick back of near-even width, and a tail spread flat like a fan rather than folded.
2. From the side: one smooth arch, with a definite downward tuck at the tail base.
3. Watch it swim. It should hold level and move deliberately. A juvenile that lists, rolls or sinks may not grow out of it.
4. Check the breathing. A raised gill rate in a shop tank is worth noticing — fast or laboured breathing covers what it can mean.
5. The wen matters least at this stage, because it arrives last. Judge the back and the tuck.
6. Read the whole shop, as choosing and bringing home a goldfish sets out, then quarantine it for at least four weeks. A ranchu going in with other fancies is exactly the case where that matters most.

Where you will find one. There are effectively two markets, and knowing which one you are in prevents most disappointment. Pet-shop ranchu are ordinary fancy goldfish sold young, perfectly good for a home aquarium, and priced accordingly. Japanese show ranchu are a graded, competitive market with prices to match, where back curvature, tail set and head are judged against a standard most keepers will never need. Neither is a better fish to live with. Buy from the first market unless you intend to show, and do not pay show prices in a shop that is not selling show fish.

Personality and behaviour

Ranchus are slow, calm and deliberate, spending much of the day near the bottom picking over sand or bare glass for food. They are not timid and quickly learn to meet the keeper at the glass, but everything they do takes time. That makes tankmate choice decisive: with other slow fancies such as lionheads, telescopes and bubble eyes, a ranchu eats and settles normally; with fantails or ryukins it is often last to the food, and with any single-tail it simply loses — chasing and bullying covers that quiet mechanism, which starves a fish without anything that looks like conflict.

Aquarium requirements

Around 100 litres (26 US gallons) for the first ranchu and 40 to 50 litres for each additional one is a reasonable working range; the tank size calculator turns your group into figures. Depth matters less than footprint: ranchus are traditionally raised in shallow tubs, and a wide, low tank suits a fish that struggles to hold position in deep or moving water. Many keepers run ranchu tanks bare-bottomed for easier cleaning, and substrate for goldfish covers the alternative if you would rather not. A wide, shallow tub is a legitimate home rather than a compromise — the tank buying guide makes that case, and for this breed it is stronger than usual.

Flow separates a good ranchu tank from a bad one. Filter for five to ten turnovers an hour but deliver it gently, through a sponge filter, a spray bar aimed at the glass or a baffled outflow, as the filtration guide explains. Keep the temperature between 18 and 24 °C (64 and 75 °F) and steady, change 25 to 50 percent of the water weekly according to nitrate, and test regularly; the water testing guide covers the routine. Decor should be minimal and smooth — aquarium decorations covers the test for anything you are unsure about, and a fish with no dorsal fin has no business near a narrow gap.

Feeding

Feed a quality sinking pellet designed for fancy goldfish as the base, soaked briefly, in two or three small meals a day. Ranchus gulp air readily at the surface, and floating food is often blamed for their buoyancy trouble, as is dry food that swells in the gut. Gel food suits them well because it is soft, moist and easy to portion; the gel food guide explains how to use it. Add shelled peas or blanched greens once or twice a week, and frozen daphnia as an occasional treat. Breeders feed heavily to build body and wen in young fish, but in a home aquarium a modest, consistent routine and clean water do more than rich food.

Common health considerations

Three problems account for most ranchu trouble. Wen infections appear as reddened, cottony or eroded patches on the hood and usually follow a lapse in water quality; the fix begins with a test and a large water change. Buoyancy problems, floating or tipping after meals, often trace to diet and gulped air, though vets find many causes; the floating guide walks through the possibilities. A ranchu that sits on the bottom with clamped fins is usually reacting to ammonia, nitrite, a temperature swing or exhaustion from current; the sitting on the bottom guide explains how to narrow it down.

Ranchus also feel the stress of transport and new tanks more than hardier breeds, so quarantine new fish, introduce them to a mature, cycled aquarium and expect a week or two of quiet before they settle. A fish that catches itself on decor during that unsettled fortnight is common enough to plan against — first aid for an injured goldfish covers the response.

What goes wrong, in order

Predictable problems, which is the useful thing about a demanding breed.

What you see	Usually	Where to look
Floating or tipping after meals	Often diet, though other causes exist	Floating upside down
Resting low, fins clamped	Water, temperature, or exhaustion from flow	Sitting on the bottom
Redness or fuzz in the wen folds	Water quality, then bacteria	Wen care
Losing condition with no visible cause	Outcompeted at feeding	Chasing and bullying
Working hard to hold position	Current, more often than illness	Goldfish filtration
Gill rate up, everything else normal	Warm water, or the water itself	Fast or laboured breathing

Five of those six are the tank, which is the short version of ranchu keeping. The breed does not need anything exotic; it needs the ordinary things done properly, and it complains sooner than a hardier fish when they are not.

Is a ranchu right for you?

It suits you if you have kept fancy goldfish for a year or two, you enjoy looking at a fish from above and would consider a tub or a shallow tank, you test water and change it on schedule without being reminded, and you find a demanding animal interesting.

It does not suit you if it would share a tank with single-tails or with quicker fancies, if the tank is deep and the flow is strong, or if you want a first goldfish — goldfish for beginners is straight about where to start, and it is not here.

And it is worth knowing what you are taking on. A dorsal-less, round-bodied fish with a hood is a long way from a wild carp, and the argument in goldfish welfare about how far selection should go is one a ranchu keeper should have read. A well-bred, well-kept ranchu is a thriving animal; an extreme one in poor water is not.

History and origin

The ranchu was developed in Japan from dorsal-less Chinese stock. English-language accounts call it a descendant of the Chinese lionhead, while Japanese sources trace it to the wen-less, dorsal-less maruko brought from China, with the wen selected in Japan; the name ranchu is first recorded in 1748. From the Meiji period Tokyo breeders laid the foundation of the modern ranchu, the steep tail drop, the compact wen and the broad, arched back, all defined for viewing from above, and Japan now has two show lines judged to different standards. A round-bodied form without a head wen, recorded in the Edo period, was lost in the Second World War and rebuilt from other stocks, and it is rare.

In Japan it is called the king of goldfish, and it has one of the most developed show cultures among goldfish: fish are judged in shallow tubs against a written standard, and top fish change hands for large sums. Ranchus bred in China and Thailand, sometimes selected for side view rather than top view, are common in Western shops.