Keeping Koi
Koi are technically domesticated Eurasian Common Carp (Cyprinnus carpio). All are mutations and colour morphs of the same species, created by man through selective breeding. The Eurasian Carp has been kept and farmed for many thousands of years. Carp are hardy and good to eat. Around 2000 years ago these fish were introduced to the Far East, soon becoming popular food fish. Eventually this led to them being kept as pets in Japan. It is reputed that Japanese farmers raised and kept their Koi in their rice fields. At some point in history, colour mutations appeared, probably black or gold specimens. These individuals were seen as a curiousity and so were not eaten, but instead kept as pets. Such Carp became highly prized and over time, some hundreds of years later have developed into over 100 colour varieties seen today.
Modern Koi are bred in vast numbers all over the world to meet the demand for them in garden ponds. Countries such as Thailand, China, Israel, South Africa, America and across Europe; although the better quality specimens still originate from Japan.
Colour Forms
There are well over 100 known colour mutations seen in Koi and the majority originating from Japan have descriptive as well as poetic names. A few of the more common mutations available in the UK are:
Kohaku
These are snow white Koi with deep red markings/patterns down their back. This red and white fish is probably the architypal Koi of Japan and good specimens are highly prized. They are very common and readily available from reputable stores.
Sanke
The Sanke is a white fish with small black patches dotted symmetrically down its back. Sanke are beautiful fish that are reasonably common.
Showa
These are similar in markings to Sankes although Showa are black fish with red and white markings. These are stunning fish with thick black markings wrapped around the fish from top to bottom, intermingled with blood red patches. Another reasonably common variety.
Koi are a beautiful addition to any garden pond, they have been called ‘living jewels’ a term which they definitely deserve.
These varieties are quite unusual since they are blue carp. Both have pale blue skin with dark blue scales and dark red sides. Both have pale coloured heads and often sport red eyes. To tell the difference between them look at the scales; Asagis have standard small scales whereas the Shusui have large mirror pattern scales. Both species are becoming more readily available but often only from good specialist outlets.
Ogons
These Koi are solid or one colour, these are beautiful metallic fish with iridescent scales and fins. Ogons come in three main colours; yellow/gold, white/platinum and orange. Ogons are a very common Koi and are readily available in many countries and are most often the Koi of choice for beginners.
Chagoi
This is another solid coloured Koi, which can be sandy brown coloured to a rich chocolate brown. Chagois do grow pretty quickly and are quite large in comparison to other varieties. Chagois are well known for their friendly nature and are often introduced to Koi ponds to calm other individuals.
These are just a small number of colour varieties that are available to today’s hobbyist. To add extra confusion, all varieties come in different scale patterns and skin types. It’s their amazing diveristy that make Koi so special.
Koi Husbandry
Koi are large and energetic fish, most will reach at least 60cms (23 inches) in two-five years. The original Eurasian carp evolved to live in lakes and large slow moving rivers. They are not very well adapted to living in small volumes of water, therefore before you consider keeping these kind of fish make sure you can provide plenty of space.
Ponds
Ponds will need to provide a volume of water no less than 4500 litres (1000 gallons). A suitable pond will also need a good surface area and a depth of at least 120cm at its deepest point. Ponds for Koi should be situated in a sheltered spot, but not below trees or shrubs that could drop leaves during the autumn and winter months.
Mechanical filtration media will need to be cleaned on a weekly basis during summer months and must only be cleaned in pond water and not tap water. Biological filter media can be rinsed through approximately once a month, again only in pond water.
To keep the water clear of nuisance algae in the pond a ultraviolet sterilisering unit can be used. Basically water is passed through this unit prior to going through the main filter; inside the unit water passes under a UVC light which is lethal to micro-organisms and algae, killing off any algae and keeping the water clear. UVC bulbs should be replaced every 12 months.
The pump which feeds the filter should be a submersible one, there are many types available through good aquatic shops. The pump should be capable of passing the volume of your pond water at least once every hour.
Plants
Plants are a good addition to any pond since they not only make a pond look beautiful but also remove toxins and produce oxygen as they grow. Traditionally plants are not grown in ponds with Koi since these large omnivorous fish eat them. If you choose tough marginal species and protect them in strong plant baskets with heavy duty mesh tops, then they’ll usually survive. Species such as Iris Leavigata and the Fleg Iris, as well as some of the large waterlily species (Nymphea Alba) tend to do pretty well.
Feeding Koi
Koi are omnivourous and practically eat anything; from aquatic insects, other smaller fish species and plant roots to leaves and seeds. Carp have a large downward pointing mouth with two short barbels either side of it which are covered in tastebuds. The bulk of their diet should be good quality Koi pellet food, there are many varieties to choose from. Try and pick a food which has a protein level of around 30 per cent. With anything above this then the fish will produce a lot of Ammonia (NH4), which will put a lot of pressure on the biological filtration; anything below 30 per cent will not allow the fish to grow and develop properly. To boost the protein level of their diet add fresh peeled prawns occasionally but only when the weather is warm since Koi digest proteins better when they’re warmer. Other things which can be added to boost variety include: wholemeal bread; chopped orange segments; chopped cleaned earthworms; frozen bloodworm; (defrosted) frozen peas.
Koi feed most during late spring through summer and early autumn. Once temperaures in the pond drop below 10°C their digestive system shuts down. They should not be fed once the temperature is at this level, any food present could rot causing all sorts of problems. During low temperatures Koi rely on fat reserves built up during the summer to survive. Never over feed Koi, they must clear up all that is fed within less than one minute or so at any one feed. During spring and autumn feed only once a day. In the summer feed little and often – approximately three to four times per day.
Koi are farmed all over the world but the majority sold in the UK are currently produced in Israel. Koi have been commercially produced in Israel for over 30 years. Every aspect of Koi production is controlled by people. Adult fish are selected for their colour and strength, they are then conditioned with good feeding and water quality. They are gently hand stripped of eggs and sperm and these are then placed into large funnel-like containers, which gently swirl them together with water. The fertilised eggs quickly hatch (within six days), these baby fish (fry) are then reared initially in small vats. Once they are stronger they are moved out into large outdoor mud ponds to mature. Throughout their lives the fish are regularly rounded up and sorted for size and colour, selecting the stronger more colourful individuals for sale. They are finally sold onto dealers around the world.
When buying Koi for your pond, make sure you only buy from reputable dealers; choose fish by carefully looking at their condition and that of their fellow tank mates. All Koi should be quarantined for at at least 30 days before being put with existing pets. This quarantine time will allow the new Koi to settle in and enable the new owner to treat the fish for any parasites or infections which may arise from the stress of moving to a new home.
A Final Word
Koi are a beautiful addition to any garden pond, they have been called ‘living jewels’ a term which they definitely deserve. These large hardy fish are reasonably easy to keep with a bit of thought; they can live for decades in captivity. Some have been known to live 40 years or more and so are a creature you can enjoy keeping for years.
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