Breeding Koi & Goldfish for Fun & Pleasure

Page Summary: It starts with a wild chase and lots of thrashing about. Yes it's spawning time in the pond. Spring with its warmer temperatures and longer day times brings along the urge of koi and goldfish to spawn. It is a combination of temperature change and daylight hours that initiate this spawning frenzy. It is an exciting time for both fish and the pond owner. Left to their own devices and if there are no plants in the pond the eggs will probably be eaten. If you want to breed some of the fish then you will need to harvest the eggs initially and then protect them and the fry until they grow somewhat. The starting point is a spawning brush to capture the eggs. Once captured the eggs must be isolated in a floating fine mesh basket (make yourself from a lump of polystyrene and fine mesh) left inside the pond, now protected from parent, cannibal fish.

The best broodstock for breeding koi

Breeding koi – and even goldfish – is an enormously rewarding and fascinating business, even if you don't do it commercially. In fact breeding koi as a hobby can be a huge amount of fun, since you don't have the responsibility of ensuring the process is financially viable.

While you certainly don't have to be a marine biologist to be a successful koi breeder, it does help to have some practical knowledge of the processes involved. In particular it helps to know what to look for when you first stock your pond with the intention of breeding koi.

The breeding process

It is a fact of life that all creatures breed. But it may come as a surprise to discover how primeval the breeding process is in the fishy world. You would be forgiven for assuming that koi were at war with one another if you weren't forewarned of the spawning process. Indeed, the same goes for golden orfes, and smaller shubunkin and even the common goldfish.

Presuming pond conditions are suitable – which includes both the quality and temperature of the water in the pond – female koi will produce fish eggs in late spring or early summer. At this time the days are also longer, another factor that will naturally stimulate koi to breed. It is also a primary factor that will ensure the fish eggs mature and hatch successfully.

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When the female koi are "ripe" and ready to lay their fish eggs, any male koi in the pond will begin bashing the females to provoke the spawning process. The aggression displayed by the male fish is legendary. Uncontrolled, they often batter the females, particularly when the number of males in a pond outnumber the ripe females. This frequently results in injury which can lead to scarring and to the loss of scales.

While nature demands that male koi are present for spawning, many commercial koi breeders separate the males from the females – at least during the breeding season. They then induce the females so that they release their eggs. Commercial breeders will usually manipulate the environment as well, for example by moving the fish under cover to spawn in water that is heated. By ensuring that the water remains at a particular temperature for a specified time, they are able to provide the ideal environment for spawning. They will also use hormones both to induce the females and to increase sperm production in the male fish.

Commercial breeders will also fertilise the fish eggs with sperm from chosen males, that way carefully controlling the species. They incubate the eggs for about five days until they hatch, and then once the fry are ready, they move them to production ponds. Here their growth can be monitored and the poor quality fry culled.

Of course if you are serious about keeping koi as a hobby, and breeding them, you should also provide both the fish eggs and fry with a suitable environment in which to hatch and then grow (as the commercial farmers do). Funnily enough, fry do best in unfiltered ponds that are full of plankton that they feast on. You will also find that far more fry survive and flourish if they are separated from the adult fish, even if you have selected the parents. Nevertheless the challenge for any breeder – whether a hobbyist or commercial koi farmer – is to choose suitable broodstock from which to breed.

What to look for in koi broodstock

Koi come in a variety of colours including black, white, yellow, orange and red. There are also metallic colours, largely silver and gold. While single coloured koi are sometimes produced, these are generally considered to be of a "poor" quality. The exception is the plain metallic colours. Furthermore, it isn't just a combination of colours that is important (red, white and black for example), but also the patterns and markings on the fish.

There are numerous books on koi that have full colour photographs of the different types, showing exactly what markings to look for. Generally you will pay much more for a well marked fish than one that is not a very good example of that particular variety. However, as any experienced and knowledgeable koi breeder will tell you, some of the best broodfish are in fact not great examples of the variety, yet they produce brilliant offspring. Similarly, buying an expensive specimen that meets all the requirements of a good bloodline will not guarantee that the babies it produces will meet the same standards.

Another factor to consider is that while inbreeding often produces some beautifully patterned koi, it can also result in eventual health problems.

On this site we don't pretend to be "Koi Crazy" despite the fact that you will see I refer to koi more often than not.

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Ready for Breeding Koi in Spring

In spring when loves comes around the koi will need somewhere to lay their eggs. In a natural environment eggs will adhere to submerged aquatic plants but in a koi pond there are not always plants because the koi tend to eat them.

You'll be amazed at how simple it can be to breed fish with the help of spawning brushes. You'll need one mature female and at least two males.

Put the brushes one above the other at the edge of the pond. Spawning usually occurs in the early morning after a night of flurried activity and can take several hours. Most of the eggs will stick to the brushes which can then be taken out of the pond and put in filtered water of the same temperature. If the eggs are not separated from the adult fish they may be eaten.