Breeding Koi is not difficult but it is difficult to do well. Koi will breed in any outdoor pond but the adults will eat the eggs so you have to be lucky to get any young.

Also you do not have to breed your fish to keep them healthy, they don’t have the urges of a 14 year old teenager, Koi Carp are calm and serene creatures which are fully capable of living a celibate, monk-like zen lifestyle.

If you don’t want more Koi just leave them and they will eat the eggs. Just watch the females don’t get too beaten up in the process.

To breed seriously you need a 2 year old male Koi and a 3 year old female Koi. Like goldfish, the male will have white spots on its pectoral fins when the mating season comes around. The male will also be more slender than the female that will have a swollen abdomen. This is the best way to sex your Koi. Again make sure it is sex spotting not white spot disease.

Image result for white spot disease koi fish
white spot disease

Koi Fish Gender

Since the adults eat the eggs, you will need to have a separate spawning pond where the mated iish are placed. Then they can be removed when the laying is complete. This saves the eggs and also allows the female(s) to rest, especially when you have a female with more than one male. Try not to use more than two males to a female although three have been used. I think it injures them too much.

Top breeders who keep complex genetic records prefer single matings of Koi. These genealogical records form a pattern for breeders to follow.

When mated and ready to spawn you will need some nesting material for the eggs to stick to. *Artificial spawning media* can be purchased and is made of nylon. This is most satisfactory and does the job well. More natural substances such as branches and water hyacinth can also be used. Any submerged media of this type will work. Get this prior to mating as you won’t have it when the time arrives.

Image result for spawning mops
A spawning mop

This will need to be in a separate pond, with much the same conditions as the main pond. It will need to be filtered, aerated and have proper shading. Don’t make the aeration too strong as a calm water environment is preferred. The shade is important as they won’t spawn if it is too hot. When mating takes place the female will play with this nesting material and the male will move into a spawning position next to the female. He forces the eggs out by bumping her while at the same time releasing sperm.

The eggs are very sticky and the movement sends them everywhere. The eggs should get on the media as they are very sticky. They should be separated afterwards to give the female time to rest. Be careful with handling as the slime coat may have worn off with the activity. Check the female out for any damage to the fins or tail. Keep the eggs moist when you move them to the hatchery tank. If you leave them in the mating tank change some of the water as it will be ditty from breeding. The eggs develop from; single cell and fertile eggs will be clear. They should begin to hatch on the mth day and all should be hatched on the sixth.

Wben hatched you must remember that the normal filter will suck them in so you have to turn it off before the hatch. This will give you some problems with clean water that must be regularly changed by careful water exchange through filters such as a Nylon stocking. Don’t overfeed, as this will kill the young via dirty water, in fact no food is required for the first day as the young fish can live off the nutrients contained in the egg sac.

If you breed Koi fish you’ll have to cull as the number of young can be as high as 50,000. You can only feed so many and it can be hard to get rid of them. Try to keep the colour you are breeding for. This can be hard to do. Don’t breed your fish if you don’t think you are able to cull.

Diseases of Koi
Koi get the same types of diseases as other types of fish but are relatively hardy in most circumstances. The types of diseases they are vulnerable to include:

  1. Bacterial
  2. Viral
  3. Fungal
  4. Parasitic

These diseases are usually caused by stress – the biggest killer of all fish.

Image result for stressed fish
stress is often the biggest killer of all fish!

You must minimize the stress endured by your fish, stress in Koi fish releases free radicals, you have to minimize the stress on your fish as any pathogens that are present will break out under stress.

As with other fish, you need to be aware of the cause of this stress. In koi, the main causes are:
* dirty water
* poor feeding habits
* lack of/poor oxygenation
* crowding
* harassment by pets/predators
* high temperatures
* poor handling
* chemical residues
* power failures

Try to minimize these problems. For example, in a power failure while you may not be able to use the filter, you can run a battery operated aerator to keep up the oxygen levels.

Most problems have the same cures as for other types of fish. (expand this section onto fish diseases)

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