Gold Ogon Koi (Cyprinus carpio)

Bring a metallic gold koi to your pond

The gold ogon koi is pure, shining gold. It carries no pattern and no second colour, just an even metallic sheen on every scale, on its head and through its fins. In a pond it glows like a coin under the water, and it is often the first fish a visitor notices. If you want one koi that reads clearly from a distance and lights up a dark-lined pond, a gold ogon koi is one of the most rewarding choices you can make. It has the standard short fins of a normal koi.

Ogon are the single-colour metallic koi. The Wikipedia article on koi lists gold, platinum and orange as the colours most commonly seen, with cream very rare, and records that the variety was developed by Sawata Aoki in 1946 from wild carp caught in 1921. Practical Fishkeeping describes the metallic yellow form, Yamabuki Ogon, as the golden jewel of any pond, with a bright metallic sheen that looks almost as if it is glowing.

Like all koi, the gold ogon is an ornamental carp. It is listed as Cyprinus carpio, the common carp, as FishBase and UK law treat koi; Wikipedia notes that most koi breeds actually descend from the Amur carp, Cyprinus rubrofuscus, domesticated in Japan in the early 19th century. The name does not change its care.

Tell a gold ogon from other yellow koi

Practical Fishkeeping’s simple test applies to all of them: if the fish looks shiny, it belongs to a metallic variety. Browse the rest of our koi and carp category to compare colours.

Check what arrives in the bag

One purchase supplies one live gold ogon koi at 3–4 inches (roughly 8–10 cm). The price is for one fish. Sex is not chosen or guaranteed. The photographs show the variety rather than the fish you will receive, so expect some difference in the depth of gold and the evenness of the scales; the exact shade of gold also varies from fish to fish.

Judging quality at this size is hard. Practical Fishkeeping notes that koi under about six inches are difficult to identify and that size and lineage both play a part. For a metallic koi, look for an even scale pattern, a clean head and fins with a strong metallic lustre.

A 3–4 inch koi is only at the start of its growth. OATA says koi can grow to 75 cm, and FishBase records a maximum of 129 cm total length for the species and a common length of 31 cm. FishBase also gives a maximum reported age of 38 years, so buying a koi is a long-term commitment.

Decide how many koi your pond can take

• FishBase notes common carp kept in groups of five or more; koi are usually kept with other koi.
• Count every fish in the pond at its adult size, not its size today, and leave room for growth.
• Breeding stresses females, and OATA says it is worse when males outnumber females; as young koi cannot be sexed, keep an eye on the group as it matures.
• Check our delivery information for dispatch days and the Live Arrival Guarantee before ordering.

Size the pond for a 75 cm fish

OATA recommends a pond of 4,500 litres or more for koi, with part of it deeper than 90 cm. It describes koi as slightly more delicate than other pond fish, needing good water quality with minimal fluctuations, and says they require specialist ponds and equipment: filtration systems, pumps and UV units that keep the water clear by reducing floating algae.

The depth is there for stability. OATA explains that a deep pond holds a cool zone at the bottom in hot weather and a warmer one in freezing winters, which spares koi from sudden temperature swings. Shallow ledges around the edge give you room for marginal plants, which add oxygen, take up pollutants and support the small creatures fish forage for.

Measure before you buy

Those are straight-sided figures; sloping sides and shelves hold less. Use our volume calculator for your own measurements and our stocking calculator to judge how many adults the pond can hold.

Place and plant the pond well

OATA suggests a pond that gets some sunlight, which warms the water in spring and summer and helps plants grow, but warns that too much sun can overheat the water and drive algae. Keep the pond clear of overhanging trees that drop leaves; where that is impossible, fit an autumn net. A net over the pond also protects koi from herons and other predators, especially in winter when plants give little shelter, and stops newly added fish jumping out.

Plant the margins generously. OATA notes that live plants provide oxygen, remove pollutants and provide food, directly or by supporting tiny organisms. Because it links too much sunlight and excess nitrate and phosphate to algae such as blanket weed and green water, plants that shade the surface and use up nutrients help on that front too.

Keep the water stable

Koi are carp, and carp are tough: FishBase gives the species a range of 3–35°C, pH 6.5–9.0 and 10–15 dH. In a garden pond, though, OATA asks for tighter, steadier values:

Know your tap water

Every top-up adds tap water, so know what is in it. Test it for pH, hardness and nitrate, compare it with the targets in our water matcher, and read our water chemistry guide if a reading puzzles you. Always treat new water with a conditioner that removes chlorine and chloramine; our water care range has conditioners and test kits. OATA recommends testing pond water weekly, especially while the pond is new.

Run the filter all year

The filter is the heart of a koi pond. It turns toxic ammonia and nitrite into far less harmful nitrate, and OATA warns that adding fish too quickly causes “new pond syndrome”, when the filter bacteria cannot keep up; our nitrogen cycle guide explains why a filter needs time to mature. How often to clean it depends on its type, size and the number of fish, so follow the maker’s advice, and watch the flow as a sign that it is working.

Keep a simple routine

1. Each week: test the water and look at every fish as it comes up to feed.
2. When the filter needs it: rinse the media lightly in pond water, never under the tap, so the bacteria survive.
3. Each autumn: remove dead leaves and plants and trim the marginals before they rot.
4. Each winter: keep a hole in any ice with a pond heater or floating device; the RSPCA warns never to smash the ice.
5. Each year: replace the UV bulb, as OATA advises, unless the maker says otherwise.

Feed a gold koi through the year

In the wild, carp eat bottom-living invertebrates and plant material, FishBase records, so koi are omnivores and take pellets readily. OATA sets out a seasonal pattern for pond fish: a higher-protein food in summer to build reserves, a lower-protein, more digestible wheatgerm food as the water cools, and possibly no food at all once the water falls below 8°C. It also notes that colour-enhancing foods can bring out a fish’s colour, and that pellets come in different sizes to suit different fish. Feed only what the koi eat within a few minutes, once a day.

Plan a feeding calendar

Bring it home in any season

When the fish arrives, follow OATA’s floating-bag method. Keep the bag out of bright light, float it on the pond for 10 minutes so the temperatures even out, then add small amounts of pond water before releasing the koi with as little bag water as possible. Our guide on how to acclimatise new fish takes you through it.

In the colder months the pond may be much colder than the bag. Then we suggest settling the koi in a quarantine tank indoors and moving it outside in spring. A tank is a short-term solution only: FishBase says carp are not recommended for home aquariums. Quarantine is worth doing whatever the season, because Cefas warns that fish carrying koi herpesvirus do not always look ill.

Check the first fortnight

• Day of arrival: breathing, fins and balance; release quietly and keep the pond netted.
• First days: offer a little food only if the water is above about 8°C.
• Day 7: test ammonia, nitrite, nitrate and pH, and correct anything out of range.
• Day 14: the koi should be swimming with the others and feeding confidently.

Mix it with calm pond fish

OATA says most pond fish get on with each other, though they may need slightly different conditions. A gold ogon looks striking next to patterned koi such as our Grade A Premium Koi Mix, and it shares a pond happily with single-tailed goldfish such as the Bronzed Comet Goldfish, with the Golden Orfe (OATA advises keeping orfe in groups of four or five) and with tench.

Screen each companion

Our tank mates tool checks a planned mix, and our guide to cold water fish for sale compares the main pond species. See everything in our goldfish and coldwater fish range.

Know the notifiable diseases

Two virus diseases of koi must be reported by law in England and Wales. Koi herpesvirus (KHV), according to Cefas, is a contagious disease of common carp, including koi, that can cause high losses. It appears at 16–29°C, often after stress, is endemic in Great Britain and has no treatment. Spring viraemia of carp (SVC), says Cefas, affects koi, goldfish and other carp, is most active at 11–17°C, and Great Britain is free of it. Suspected cases of either must be reported to the Fish Health Inspectorate at Cefas immediately.

Match each sign to a response

Cefas advises never buying fish of unknown origin and notes that these viruses travel with fish, water and equipment, so quarantine every new fish and use separate nets for each pond.

Expect a long life, and leave breeding to nature

A healthy koi in a good pond lives for decades; FishBase gives 38 years as the maximum reported age for the species, while much older ages claimed for individual koi in Japan are not well verified. Koi may spawn in late spring and early summer: FishBase notes carp breed at 15–20°C, lay sticky eggs on plants that hatch in about four days, and that a spawning female is usually followed by several males. OATA warns that koi can be aggressive while breeding and can injure, or even kill, females, especially in a pond with more males than females. And Wikipedia notes that koi revert to wild colouring within a few generations if they breed freely, so pond-bred young seldom match their gold parent.

Answer gold ogon koi buying questions

What is a gold ogon koi?

A koi of one metallic colour, gold from head to tail, with no pattern. Ogon are the single-colour metallic koi, and gold is one of the three colours most often seen, with platinum and orange. Practical Fishkeeping calls the metallic yellow form, Yamabuki Ogon, the golden jewel of any pond.

What is the difference between a gold ogon and a yellow koi?

The shine. Practical Fishkeeping notes that a koi that looks shiny belongs to a metallic variety. A gold ogon has metallic skin and fins; a matt yellow koi, such as our Banana Koi, has the colour without the metallic lustre.

How big will a gold ogon koi grow?

OATA says koi can reach 75 cm, and FishBase records 129 cm for the species, with a common length of 31 cm. The fish is supplied at 3–4 inches, so plan the pond for an adult of 60 cm or more.

How large a pond do I need for koi?

OATA recommends at least 4,500 litres, with part of the pond deeper than 90 cm, and specialist filtration, a pump and a UV unit. As a guide, a regular pond 3 m long, 2 m wide and 1 m deep holds about 6,000 litres.

Can I keep a gold ogon koi with goldfish?

Yes, with single-tailed pond goldfish such as comets and shubunkins. OATA says most pond fish are compatible. Keep twin-tailed fancy goldfish indoors in an aquarium instead.

Do I need a licence to keep koi in my garden pond?

No. GOV.UK guidance for England and Wales says you do not need a licence to keep common carp, which includes koi. It is illegal to release them into the wild.

When should I stop feeding my koi in winter?

OATA suggests switching to a wheatgerm food as the water cools and says it may be better not to feed at all below 8°C. Restart slowly in spring.

What is koi herpesvirus?

A notifiable viral disease of carp, including koi, that can kill many fish. Cefas says it occurs at 16–29°C, has no treatment and is endemic in Great Britain. Report a suspected case to the Fish Health Inspectorate at Cefas.

Consult the care references

• OATA: How to look after pond fish and the printable care sheet — koi pond size and depth, equipment, water values, seasonal feeding, compatibility and breeding.
• Practical Fishkeeping: How to identify your koi carp — Yamabuki Ogon and how to tell metallic koi apart.
• Wikipedia: Koi — the ogon variety, its colours and history, ghost koi and koi ancestry.
• FishBase: Cyprinus carpio — size, age, water ranges, wild diet, spawning and aquarium notes.
• Cefas (GOV.UK): Koi herpesvirus and Spring viraemia of carp — signs, prevention and the duty to report.
• GOV.UK: Introduce or keep non-native fish — koi need no licence in England and Wales.
• RSPCA: Caring for pet fish in winter — keeping a pond ice-free safely.
• Tropical Fish Co delivery policy — current dispatch days and Live Arrival Guarantee terms.