Red and White Butterfly Moor Goldfish (Carassius auratus)

Choose a butterfly moor goldfish with a wing-shaped tail

The Red and White Butterfly Moor is a butterfly moor goldfish, a fancy form of Carassius auratus bred for two features at once: large protruding eyes and a fully divided double tail that opens out flat, like a pair of wings, when you look down on it. This fish is metallic red and white, with bold red patches over a shining white body and red streaks running out through the white fins.

Butterfly-tailed goldfish have been bred in the Far East for longer than they have been kept in Britain, where the Bristol Aquarists’ Society says they have been seen for around twenty years. In the Far East they are sold as butterfly telescope goldfish or butterfly moors, and in the USA simply as butterfly goldfish. The society introduced the first UK show standard for the butterfly in 2021.

Check the names before you compare

Because the UK Moor standard accepts black fish only, a red and white fish is not a Moor in the show sense, even though “moor” is part of its trade name. Its care is the same as for any telescope-eyed fancy goldfish. If you prefer the classic velvet-black form, see our Black Moor goldfish, and for a red and black fish with a conventional twin tail, see the Red and Black Telescope Moor. All of our fancy varieties are in the fancy goldfish category.

Know what one purchase supplies

One purchase supplies one live Red and White Butterfly Moor of about 4–5 cm. That is a young fish, not an adult. The UK standard sets a minimum body length of 5.5 cm before a butterfly is judged, so the eyes, body depth and the full spread of the tail are still developing when it arrives. Order the number of fish you intend to keep, and plan the aquarium for all of them as adults.

Sex is not specified. OATA describes how mature males develop small white tubercles on the gill covers and pectoral fins in spring and summer, while females have deeper bodies, but a young 4–5 cm fish may not show either sign yet.

Expect each red and white pattern to be different

Red and white goldfish are variegated, which means the red and white areas fall differently on every fish. The gallery images show the colour form and are based on a reference picture of it; they do not show the individual you will receive. The UK butterfly standard asks for a similar pattern on each side of the body, but pet-quality fish vary, and a young fish can still change as it grows.

According to the Bristol Aquarists’ Society, the white areas of a goldfish carry no pigment cells, while the red areas are rich in red pigment cells. Light is the strongest outside influence on colour: goldfish kept in dim conditions look pale, and good lighting brings out saturated reds. Diet plays a smaller part. Red and white goldfish have a long history, first developing in domestic ponds in China during the Southern Song dynasty (1127–1279).

Give the adult butterfly moor room to spread its tail

OATA expects fancy goldfish to reach no more than about 20 cm, and Practical Fishkeeping gives telescope-eyed goldfish about 20 cm of body length, not counting the fins. FishBase gives the species as a whole a maximum of 48 cm in total length; the care sheets give the figures for short-bodied fancy forms. Plan the aquarium for a 20 cm adult with a broad tail, not for the small fish that arrives.

OATA asks for at least 100 litres for the first adult fancy goldfish and 50 litres more for each extra adult. The RSPCA gives at least 60 litres per goldfish and says bowls and small decorative tanks are unsuitable. Practical Fishkeeping suggests a tank of at least 120 × 60 cm for three adult telescopes in the long term, and points out that depth matters less than floor area. Where the figures differ, use the larger one.

Work out the volume for your group

As a worked example, a 120 × 60 × 45 cm aquarium holds about 324 litres before gravel and decor take their share, which comfortably covers OATA’s 200 litres for three adults. Our tank volume calculator converts your own measurements into litres, and the stocking calculator helps you check a mixed group before you buy.

Set up an open, smooth tank you can view from above

The butterfly tail is held almost horizontally. From the side you see it nearly edge-on; from above, the two halves spread out like open wings, with the lower lobes turning forwards towards the head. Practical Fishkeeping notes that an open-topped 120 × 60 × 45 cm tank lets you enjoy telescope-eyed goldfish from above, and a low, wide aquarium placed where you can look down into it shows this variety at its best.

The protruding eyes are the part most easily hurt. OATA warns against decor with sharp or rough edges because it damages delicate eyes and long fins, and Practical Fishkeeping gives the same warning about sharp ornaments and spiky plants. Keep the floor area open so the fish can turn its wide tail without catching it on anything.

Check the layout in four steps

1. Substrate: use small, round, inert gravel that the fish can sift and mouth without it lodging in the mouth, or aquarium sand.
2. Hardscape: choose smooth pebbles and, if you like, a single water-worn piece of wood. Run a finger over every edge before it goes in.
3. Plants: none, hardy plants such as Anubias tied to wood, or soft, non-spiky plastic plants. OATA notes that goldfish may eat delicate live plants.
4. Position: keep the tank away from draughts, radiators, direct sunlight, loud noise and vibration, and use overhead lighting for a regular day and night.

Keep the water within fancy goldfish values

Goldfish are coldwater fish. OATA’s fancy goldfish values below suit this fish; FishBase gives the species a slightly wider pH range of 6.0–8.0 and a hardness of 5–19 dH, and the RSPCA gives 10–21°C. Stability matters more than chasing an exact number.

Prepare UK tap water before it goes in

Tap water differs from one UK region to another, so test yours rather than assume. Public supplies are disinfected with chlorine or chloramine, which must be removed: treat every top-up with a conditioner from our tap water conditioners and treatments, and match its temperature to the aquarium, as the RSPCA advises. A heater is normally unnecessary indoors; OATA suggests one only for a very cold room. Test your own tap water and compare it on our water matcher, and our guide to water chemistry explains what each reading means.

Filter well and keep the current soft

OATA treats a filter as essential for every goldfish aquarium, but fancy goldfish prefer gentle water movement. OATA suggests a moderate filter output or a spray bar to spread the return evenly. For telescope-eyed goldfish Practical Fishkeeping recommends an external filter rated at 1,000 litres per hour or more, an airstone, and activated carbon, because goldfish tanks can smell. A spray bar lets you run a filter of that size without pushing a wide-tailed fish around the tank.

Follow a weekly maintenance sequence

1. Test ammonia, nitrite and nitrate. OATA advises weekly tests, and more often in a new tank or after adding fish.
2. Siphon waste from the gravel while removing water. OATA advises a 25% change each week; Practical Fishkeeping suggests 50% weekly where possible.
3. Refill with conditioned water at the same temperature as the tank.
4. Rinse filter media only in water removed from the aquarium, never under the tap, so the beneficial bacteria survive.
5. Look at both eyes, the tail and the body of every fish, and note anything new.

Our article on how the nitrogen cycle matures a filter explains why the filter must be established before the first fish goes in.

Feed one measured meal a day

OATA recommends a good flake, granule or pellet made for goldfish, because goldfish need more carbohydrate than many tropical fish, with daphnia, bloodworm, brine shrimp, soft aquatic plants, blanched lettuce or thawed, shelled peas as extras. Practical Fishkeeping suggests sinking goldfish pellets for telescopes, which lets every fish feed at its own pace. Feed only what is eaten within a few minutes, once a day. Uneaten food rots and fouls the water.

Some fancy goldfish gulp air at the surface and then struggle to stay level after eating. OATA suggests trying a different food or a slow-sinking type if this happens. Our article on fish swimming sideways or upside down covers buoyancy problems in more detail.

Build one measured meal

Settle it in during the first week

Have the aquarium running and fully cycled before the fish arrives. The RSPCA advises fishless cycling for at least two weeks, until ammonia and nitrite have risen and fallen back to zero, and OATA asks you to confirm zero ammonia and nitrite before adding any fish. Add fish gradually so the filter can keep up.

Use a first-week checkpoint plan

Our step-by-step acclimatisation guide walks through the bag method with pictures, and our delivery and Live Arrival Guarantee terms explain what to do if there is a problem on arrival.

Watch the eyes, tail and balance

The eyes and the large tail are where problems show first on this variety. OATA lists the general warning signs: hanging at the surface or sitting on the bottom, colour much darker or paler than usual, faster or slower breathing, white spots, fluffy growths, damaged fins or missing scales, clamped fins, flicking against objects and loss of appetite.

Pair each observation with an action

Researchers studying telescope-eyed goldfish report that their retinas are thinner than those of normal-eyed goldfish, which is one more reason to keep the eyes clear of hazards. If you are unsure, test the water first and ask an experienced retailer before medicating.

Keep it with other slow fancy goldfish

A butterfly moor is a slow, short-bodied swimmer. OATA says fancy goldfish can be kept alone or with other fancy goldfish, but not with common goldfish, which are faster, take the food and sometimes nip fins. The RSPCA gives the same advice about single- and twin-tailed goldfish and confirms that a goldfish does not need company. FishBase, by contrast, suggests groups of five or more in tanks of 100 cm or longer, so sources differ on group size: if you keep several, add OATA’s 50 litres for each extra adult.

Screen each companion

Before adding a fish, ask four questions. Is it a twin-tailed fancy goldfish of similar speed? Will the tank still meet OATA’s volume once it is an adult? Does it share the same coldwater values? Is it free of sharp spines or a habit of nipping? If you are drawn to a comet, read our comet goldfish guide first: comets are fast, single-tailed fish that should be kept with their own kind. Our tank mates tool checks a planned mix for you, and our goldfish and coldwater fish collection lists the slow, twin-tailed varieties we stock.

Breed butterfly moors only with a plan

OATA says goldfish are best bred in a large home aquarium with two males to each female, with spawning triggered by warming the water slowly to about 20°C. Eggs are scattered over plants or a spawning mop, which should be moved to a separate tank because the adults eat eggs and fry. Eggs usually hatch in about three days, and the fry need a dedicated set-up and fry food. A 2025 study traced the telescope eye to the LRP2 gene and found it recessive to normal eyes, so young from a cross with a normal-eyed goldfish may not have protruding eyes. Fancy goldfish breeders select hard from large spawns, so plan homes for every young fish you rear.

Answer butterfly moor goldfish questions

What is a butterfly moor goldfish?

It is a fancy goldfish, Carassius auratus, with large protruding eyes and a fully divided double tail that spreads out flat like a pair of open wings when you look down on it. In the Far East it is sold as a butterfly moor or butterfly telescope goldfish; the UK show standard calls it simply the butterfly.

Is a red and white butterfly moor a true Moor?

Not in the UK show sense. The Bristol Aquarists’ Society standard limits the Moor to black fish with a broad, unforked tail. “Butterfly moor” is the trade name for the butterfly-tailed, moor-eyed type in any colour, and this one is metallic red and white.

How big will it grow?

OATA puts fancy goldfish at about 20 cm at most, and Practical Fishkeeping gives telescope-eyed goldfish about 20 cm of body length, not counting the fins. You receive a young fish of about 4–5 cm, so plan the aquarium for the adult.

What size aquarium does a butterfly moor need?

OATA advises at least 100 litres for one adult and 50 litres more for each additional adult; the RSPCA gives at least 60 litres per goldfish. Practical Fishkeeping suggests a tank at least 120 × 60 cm for three adult telescopes, and notes that an open-topped tank lets you enjoy them from above.

Why is it best viewed from above?

The butterfly’s tail is held almost horizontal, so from the side you see it edge-on. From above, the two halves spread out like wings, which is the shape the variety is bred for.

Does it need a heater?

Usually not. OATA gives 4–25°C with 15–23°C as the best range and suggests a heater only for a very cold room. The RSPCA gives 10–21°C for goldfish. A steady room temperature matters more than warmth.

Can it live with other goldfish?

Yes, with other slow, twin-tailed fancy goldfish such as ryukins, fantails, orandas and telescopes. Do not mix it with common goldfish, comets or shubunkins: OATA and the RSPCA both say the faster fish take the food and may nip fins.

Will the red and white pattern stay the same?

Every red and white goldfish is patterned differently, and a young fish can still change as it grows. Light and diet affect how strong the colours look. We cannot promise that the pattern will stay exactly as it is on arrival.

Can I keep it in a garden pond?

We recommend an indoor aquarium. OATA advises that fancy goldfish are best kept indoors, and the protruding eyes and wide tail are easily damaged and make it a slow swimmer that would struggle against pond fish.

Consult the care references

• Bristol Aquarists’ Society: Butterfly goldfish — UK butterfly standard (2021), Far Eastern names, tail and eye description, accepted colours
• Bristol Aquarists’ Society: Broadtail moor — the UK Moor standard, which accepts black fish only
• Bristol Aquarists’ Society: Goldfish information — history of red and white goldfish, pigment cells and the effect of light and diet on colour
• OATA: How to look after fancy goldfish — adult size, water values, tank volume, filtration, feeding, acclimatisation, warning signs, compatibility and breeding
• Practical Fishkeeping: How do I keep telescope eye goldfish? — tank size for three adults, viewing from above, filter, gravel, decor, feeding and companions
• RSPCA: Choosing an aquarium for pet fish — space per goldfish, temperature range, fishless cycling and water changes
• RSPCA: Keeping pet fish together — single- and twin-tailed goldfish should not be mixed
• FishBase: Carassius auratus — family, native range, maximum recorded length and species water values
• Li et al. 2025, International Journal of Molecular Sciences — genetics of telescope eyes and retinal thickness
• Tropical Fish Co delivery policy — current dispatch and Live Arrival Guarantee terms.