Calico Fantail Goldfish (Carassius auratus)

Choose a calico fantail goldfish with a pattern all its own

The calico fantail goldfish is a twin-tailed fancy goldfish, Carassius auratus, whose pearly scales are patched in orange, red and white over a soft bluish base and freckled with black. The same colours run into the translucent fins, so the divided fan-shaped tail looks speckled and almost lace-like. Because the pattern is set differently in every fish, no two calico fantails are ever the same.

Underneath the colour it is a standard fantail: a short, deep, rounded body, one dorsal fin and paired anal and tail fins. That body shape makes it a gentle, slow swimmer that suits an indoor coldwater aquarium without a heater. It belongs to the same species as every other goldfish, a member of the carp family that FishBase lists as native to East Asia, China and Japan.

Read the calico colour standard

That is how the UK fantail standard, published by the Bristol Aquarists’ Society, describes a calico fantail. Practical Fishkeeping’s breeding feature asks for a deep blue base and adds that many breeders like black body spots and black stripes in the fins; it lists too little blue and too much orange or red among the common faults. A pet calico rarely matches the show ideal exactly, and that variety is part of its appeal. Browse the rest of our fancy and coldwater goldfish range and the fancy goldfish category for other twin-tailed forms.

Know what one purchase brings

Each purchase is one live calico fantail goldfish in the size you select: 3–4 cm, 5–6 cm or 8–10 cm. The sizes are approximate. The photographs show a typical grown calico fantail; your fish will have its own arrangement of patches and spots, and the balance of orange, white, blue and black will differ.

Choose a size with the pattern in mind

The Bristol Aquarists’ Society explains that all goldfish hatch in a dark wild-type colour and reach their adult colours as black pigment cells are gradually lost, which is why the pattern of a small calico can still change. Before you order, have the aquarium set up and matured, and read our delivery information and Live Arrival Guarantee.

See how nacreous scales create the calico look

Goldfish scales are transparent; the finish comes from a reflective layer of guanine crystals underneath. The Bristol society describes three scale types. Metallic scales have the full reflective layer and look like burnished metal. Nacreous scales have only part of it and look like dull mother-of-pearl. Matt scales have none and look flat. A calico goldfish is covered mainly in matt and nacreous scales with a few fully reflective ones, which gives the soft, pearly sheen and lets the blue and violet tones show through.

Expect the colours to evolve

• Black spots: Paul Green, writing in Practical Fishkeeping, notes that black is not a dominant colour in goldfish and often disappears over time, and that the warmer the fish are kept, the faster it can go.
• Overall shade: the same article says goldfish often become whiter with age.
• Light: the Bristol society notes that dim tanks give pale fish, while bright conditions bring out strong, saturated colour.
• Diet: red and orange pigment depends on carotenoids, which fish must get from food.

So a calico kept at the cooler end of its range, under good light and on a varied diet, has the best chance of holding its contrast, though some change over the years is natural and not a health problem.

Give a round-bodied fish enough water

OATA, the UK ornamental fish trade association, states in its fancy goldfish care sheet that fancy goldfish usually stay under 20 cm and often live six to eight years. It asks for at least 100 litres for one adult and about 50 litres for every further adult. The RSPCA uses a different rule, 2 litres of water per 0.5 cm of goldfish and never less than 60 litres each, which asks for more water once you keep two or more full-grown fish. Plan for whichever figure is larger.

Check a few common tank sizes

The volumes are simple length × depth × height before gravel and décor, so the real water volume is a little lower. Work out your own aquarium with our tank volume calculator and check the full adult group in the stocking calculator. OATA recommends indoor aquaria only for fancy goldfish, although a Bristol society breeder keeps fantails in outdoor ponds; for a pet calico, indoors is the safer choice.

Set up soft furnishings and a gentle current

Round-bodied goldfish are not strong swimmers, and their long, thin fins split easily. OATA asks for gravel or sand, décor without sharp or rough edges, and a gentle current, achieved by turning the filter down or using a spray bar. Practical Fishkeeping recommends small, round, inert gravel the fish can sift and mouth safely, smooth pebbles, water-worn wood, and either hardy plants such as Anubias attached to wood or non-spiky plastic plants.

Run a snag test before the fish goes in

• Draw a pair of tights over every ornament and piece of wood; anything that catches will catch a fin.
• Check that cave openings are wide enough for a fish twice the size of the one you are buying.
• If you use a heater, fit it with a guard, and make sure the filter intake cannot pull in a trailing tail.
• Leave a clear swimming area along the front of the tank.
• Fit a lid, which OATA recommends, and overhead lighting for a regular day and night.

Keep the aquarium away from radiators, draughts and direct sunlight, which all cause temperature swings, and give it eight to ten hours of light a day, the RSPCA’s suggestion for most aquarium fish.

Hold the water in the goldfish range

Goldfish adapt to a wide range of water, so stability matters more than chasing exact numbers. The sources give slightly different ranges:

Compare the published values

We suggest 15–21°C, where OATA’s best range and the RSPCA’s range overlap; it also helps the black spotting last. Treat every water change with a dechlorinator from our tap water conditioners, because UK tap water contains chlorine or chloramine. Test your tap water’s hardness and pH, enter the readings in our water matcher tool, and read the guide to water chemistry if a value looks unusual.

Keep the water clean with a weekly routine

A filter is always essential for goldfish, says OATA, and the aquarium should be matured before any fish goes in. The RSPCA recommends a fishless cycle of at least two weeks, testing every other day until ammonia and nitrite have risen and fallen back to zero; our article on how the nitrogen cycle works explains each stage. For a group of three adult twin-tailed goldfish, Practical Fishkeeping suggests an external filter of at least 1,000 litres per hour with an airstone.

Tick off the weekly jobs

1. Test ammonia, nitrite and nitrate and write the results down.
2. Siphon the gravel with a self-starting gravel cleaner while you drain the water.
3. Replace at least 25% of the volume (OATA); Practical Fishkeeping suggests up to 50% for goldfish.
4. Dechlorinate the new water and bring it to the aquarium temperature before adding it.
5. Squeeze filter sponges in the old tank water when they clog, never under the tap.

Feed a varied diet in small portions

OATA advises a food made for goldfish, as they need more carbohydrate than many other fish, fed once a day in an amount that is eaten within a few minutes. Live or frozen foods and vegetables, such as daphnia, bloodworm, brine shrimp, aquatic plants, blanched lettuce and thawed, shelled peas, add variety. Round-bodied goldfish sometimes gulp air while feeding and lose their balance for a while afterwards; OATA suggests a different or slow-sinking food, and our article on fish swimming sideways covers what to check.

Plan a week of meals

Whatever you feed, give only what is cleared in a few minutes and net out leftovers. Goldfish beg constantly, but extra food simply turns into ammonia.

Settle the new fish in calmly

Introduce your calico fantail only when ammonia and nitrite read zero. OATA’s floating-bag method is to dim the aquarium lights, float the unopened bag for about 10 minutes, then add small amounts of aquarium water to it over up to 20 minutes before releasing the fish with as little bag water as possible. Our step-by-step acclimatisation guide shows each stage.

Check in through the first week

• Day one: keep the lights low and do not feed until the next day.
• Days two and three: offer small sinking meals and check the fish is upright and feeding.
• Days four to six: look at the fins and skin each day for splits, spots or cloudiness.
• Day seven: test the water and carry out the first weekly change.

Mix calico fantails only with gentle goldfish

Calico fantails are peaceful and do best with other slow, fancy goldfish. OATA advises against keeping fancy goldfish with common goldfish, which swim faster, take most of the food and sometimes nip fancy fins. Practical Fishkeeping says fantails and ryukins are as easy to keep as telescopes and that the three mix well, while the delicate, long-finned British veiltail is better left out of such a group.

Screen each tank mate

From our range, the Red and Black Oranda Goldfish, the Blue Oranda Goldfish, the Red and White Ryukin Goldfish and the Mixed Long-Fin Goldfish share its needs. The single-tailed Bronzed Comet Goldfish belongs in a separate, larger set-up; our guide to comet goldfish covers their care, and the wider goldfish category lists our other single-tailed fish. Run any combination through our tank mates checker before you buy.

Spot health changes early

OATA lists the signs of a healthy fish: clear, bright eyes, undamaged fins, intact scales, no ulcers or bumps, normal swimming and steady breathing. Warning signs include clamped fins, flicking against gravel or décor and shimmying on the spot.

Match each sign with a first step

Fading black spots on their own are not a symptom; as explained above, black often fades naturally over time.

Understand how calico colour is inherited

Calico colour does not breed true. The Bristol society records that pairing two calicos gives roughly 50% calico young, 25% pink, matt-scaled fish and 25% bronze, fully metallic fish. Some calico-type goldfish, known as midnights, even start calico and turn black as they age. That is part of why each calico fantail is unique and why breeders raise many fish to keep a few; one Bristol breeder keeps about 20 fish from roughly 3,000 fry a year.

In the breeding season mature males show small white tubercles on the gill covers and pectoral fins, and females look deeper-bodied. OATA suggests two males to each female and a slow rise to about 20°C after a partial water change to trigger spawning, with eggs hatching in about three days; Practical Fishkeeping’s fantail breeder uses three males to each female at about 17°C over Hornwort. The parents eat their eggs, so the eggs must be moved to a separate aquarium.

Answer Calico Fantail Goldfish buying questions

What is a calico fantail goldfish?

A twin-tailed fancy goldfish, Carassius auratus, with calico colouring: a pearly, bluish base covered in patches of orange, red, white and other colours and spotted with black. The pearly look comes from nacreous scales, which reflect less light than ordinary metallic goldfish scales.

Why does every calico fantail look different?

The pattern is laid down differently in every fish, and even calico parents produce mixed young: the Bristol Aquarists’ Society says about half come out calico, a quarter pink and a quarter bronze. No two calicos are identical, so the fish you receive will not match the photograph exactly.

Will the black spots stay?

Not always. Practical Fishkeeping notes that black is not a dominant colour in goldfish and often fades over time, faster in warmer water. Keeping the aquarium at the cooler end of the range and giving good light helps the colour stay bold.

How big does a calico fantail grow?

Fancy goldfish usually stay under 20 cm, according to OATA, and often live six to eight years. The Bristol Aquarists’ Society gives about ten years for fantails.

What size aquarium does it need?

At least 100 litres for one adult and about 50 litres more for each extra adult (OATA). The RSPCA rule of 2 litres per 0.5 cm of fish asks for more once you keep two or more adults, so plan for the larger figure.

Does it need a heater?

Normally not. OATA’s range is 4–25°C, best at 15–23°C, and the RSPCA gives 10–21°C, so a room-temperature indoor aquarium suits it. Only fit a thermostatic heater if the room gets very cold.

What does a calico fantail eat?

A sinking goldfish pellet or stick once a day, only what is eaten in a few minutes, plus daphnia, brine shrimp, bloodworm and shelled peas for variety. Avoid overfeeding, which pollutes the water quickly.

Which fish can live with it?

Other slow fancy goldfish of a similar size, such as other fantails, ryukins and orandas. OATA advises against common goldfish, which outcompete fancy varieties for food and may nip their fins.

Which size will I receive?

One live calico fantail in the size you choose: 3–4 cm, 5–6 cm or 8–10 cm. Smaller fish are still developing their colour and fins.

Consult the care references

• Bristol Aquarists’ Society: Fantail — the UK fantail standard: body and tail proportions, permitted colours, show size and one breeder’s rearing and selection routine.
• Bristol Aquarists’ Society: Goldfish information — goldfish history, scale types, how colour develops, red pigment and diet, and how calico colour is inherited.
• Practical Fishkeeping: How to breed fantail goldfish — fantail ideals and faults, colour notes and a step-by-step spawning method.
• Practical Fishkeeping: Will my red, black and white goldfish lose the black colour with age? — why goldfish colour changes with age and why black markings often fade.
• OATA: How to look after fancy goldfish — UK trade guidance on fancy goldfish size, aquarium volume, water values, filtration, feeding, introduction, health signs, companions and breeding.
• Practical Fishkeeping: How do I keep telescope eye goldfish? — aquarium size, filtration, gravel, plants and water changes for twin-tailed goldfish such as fantails.
• RSPCA: Choosing an aquarium for pet fish — UK welfare guidance on aquarium size per goldfish, temperature, heaters, cycling, lighting and bowls.
• FishBase: Carassius auratus — scientific name, native range, maximum size and age, and water values for the species.
• Tropical Fish Co delivery policy — current dispatch days and Live Arrival Guarantee terms.