I have breed some Koi and Goldfish, and I am currently looking into trying my hands at Tench, Orfe and Rudd.
You could cross breed a kohaku and a Yamabuki for instance which will probably probably produce only ghost and black koi. (Another way to breed Ghosts, abit more challening though, or you could just do it normally) Remember that male genes tend to be dominant in any pairing. Always select adult fish only to ensure successful spawnings. Once you have found a pairing that gives some good fish ? keep it. If you find a pairing that produces stunning fish that look like show winner, give them all to me!!
First you need to sex the fish, females, especially in season are far more rounded than male fish which tend to be slim at all times. The pectoral fins of male fish tend to be larger and more pointed than the females, but this is by no means always the case. I find the only sure way to sex fish is to watch the fish. The ones that lay eggs are female, the ones that chase are the males !!!
Spawning usually takes place 1-3 days after introducing male to the female. It can take place at any time of day or night, unfortunately, typically spawning seems to happen around two in the morning. Spawning can be triggered by temperature changes, change in water conditions, introducing new fish or barometric pressure changes.
Separate males and females for at least one month before you intend to spawn the fish. Provide a reasonably small pond, ideally 2 x 3 x 1 metre deep. Or use a spawning net in your main pond. Don?t feed the parent fish for a few days before you expect the fish to spawn either. Prepare your growing on ponds.
Koi will spawn when the water temperature reaches around 18+. As always, you need to ensure prime water conditions with zero ammonia and nitrates. To achieve and maintain the necessary water temperatures earlyish in the season (late May) it is a good idea to provide heated conditions so that you can achieve a spawning as early as possible to maximise the length of the growing season. I recommend using purpose made spawning ropes. These are soft and easy to handle. Don?t use blanket weed ? it is too difficult to collect the eggs without damaging them. A good quantity of media is required to collect all the eggs and encourage spawning IME. Remove eggs as soon as they are laid to prevent parents eating them. This is obviously easy to do if you have used spawning ropes. Move eggs on ropes to a separate tank for hatching. This should contain water of approximately the same temperature as the spawning pond and should be well oxygenated. It does not however need to be filtered. Eggs introduced straight into growing on ponds are vulnerable to predators such as snails, tadpoles and dragon fly larvae etc. Having worked so hard to achieve the spawning in the first place, don't use them as a food source for the local pond wild life!
Obviously this is if you are very serious. You change the procedure to what you think is best, you may want to put them in the parents pond after they have hatched etc.
Good Luck
Ryan