Metallic Koi are probably the most eye-catching of all koi varieties. Whether it is their resemblance to bars of platinum or gold, or the glint of their flashing pectoral fins, metallic koi will always be found at the top of many pond owners’ shopping lists.
Their resplendent metallic lustre is created through an abundance of a particular type of colour cell that are excellent reflectors of light. Metallic koi pack in these reflective iridocytes into their skin, at the expense of the more intensely coloured chromatophores (or colour cells). Hence, these koi will rarely exhibit the reds and blacks to the same depth and intensity as equivalent non-metallic koi.
Because of the relatively simple colouration of metallic koi (particularly in pure and unpatterned metallics), they are judged on very particular criteria. The shape and proportion of their body, the depth of the metallic sheen (referred to as lustre) and the clarity of the head (does it have any blemishes?) will all count towards the quality of a metallic koi.
Metallic koi are classified into 3 groups, on the strength of their pattern (or lack of it).
The three classes of metallic koi. 1. Hikari Muji. – Single coloured metallic koi. Magnificent in their simplicity, koi in this class are often referred to as the Ogons. Their impressive livery can make the purist and most unblemished of Ogons outshine the other koi in a pond, particularly in bright spring-like sunshine and when contrasted against the darker backdrop of a pond.
Ogons are a lively choice, particularly when small, as a handful will add sparkle and vigour to the ambience of a koi pond. Metallic koi also tend to have the appearance of being ‘busier’ and less restful than non-metallic koi and make a worthy choice, adding contrast in colour and behaviour with other koi varieties.
The single coloured metallic koi belonging to Hikari Muji can be divided loosely into 2 groups.
a. Pure Ogons, where scales, finnage and head exhibit the same colouration. Specimens include Yamabuki Ogons (yellow), Purachinas (platinum), Nezu Ogons (Short for Nezumi = mouse) mousy/silver coloured koi or Orenji Ogons, surprisingly coloured orange.
b. The second group of Ogons are the Matsubas. Being an Ogon, these are mono-coloured koi but with Matsuba features, where each scale has a darkened centre. Nevertheless, as the head is scale-less, these koi maintain the clear unblemished metallic livery of the Ogon on their head. The prefix given to a Matsuba relates to its colour. For example, a Gin Matsuba is a Purachina with a Matsuba scale pattern whereas the Kin Matsuba is the same but on an Orenji Ogon.
2. Hikari Utsuri The Showa and Utsuri varieties are highly regarded as they are the only traditional varieties of koi with their own metallic classification. (That is, metallic Kohaku or Sanke, are put into the more general group of Hikari Moyo – all those varieties of more than 1 colour). A simple way of describing Hikari Utsuri is to imagine what a cross between an Ogon and a Showa or Utsuri would produce. Unfortunately, for the reasons discussed earlier, the colours and definition of Hikari Utsuri are rarely as deep as a pure Showa or Utsuri. A price worth paying for that added metallic lustre?
Varieties belonging to this class include: Kin Ki Utsuri and Gin Showa (where Kin and Gin prefixes denote gold and platinum respectively.
3. The remaining group of metallic koi belong to Hikari Moyo. These are the patterned metallic koi (excluding Hikari Utsuri and Matsuba Ogons). Basically, if it is patterned and metallic, it falls in this ‘catch-all’ group. Specimens include metallic Kohaku, (Doitsu examples are known as Kikisui), Gin Bekkos (Metallic white koi with black markings) and Kujaku (a fish that resembles a metallic kohaku, but with less intense colouration).
There are far more varieties in this class than the other two metallic groups as they include so many different varieties with a metallic lustre. My particular favourite is a very clean Doitsu Hariwake, with two contrasting colours.
In summary, metallic koi are extremely popular as they offer us a different kind of colour. Generally, metallic koi are easier to breed and farm, being produced in large numbers, making them available at reasonable prices. Metallic koi are not an end in themselves as they can be used (particularly the Ogons) to produce metallic forms of other varieties, adding yet more dimensions to a koi collection.