Whats the best way to raise Koi carp for breeding?
A massive pond. The minimum stocking quoted by most koi keepers is one fish per 1000 gallons of water. This gives the fish a chance to grow to their maximum size potential and be as healthy as possible. Even so, the pond will still need an excellent filtration system, since koi/carp in general are messy fish.
One fish per 1000 gallons is a bit extreme. I have heard 10 gallons per inch of fish, so in other words 250 gallons for a 25 inch fish.
Then you know nothing about koi if you think that will work for them. Do your research before making suggestions about a species you do not know how to care for. Koi stocking is not the same as tropical fish in an aquarium. Even goldfish stocking is not he same as little dither fish.
Perhaps reading a discussion on a Koi forum with people far more experienced than you might help. Everywhere with experienced koi people quote that 1000 gallons is necessary for mature koi. Do you know how large an adult koi is? How much waste they generate? How high their oxygen requirements are? They are very demanding fish when it comes to the resources a body of water has to offer.
I have kept koi before.
Koi will not reach their full size potential nor be healthy enough for breeding inside of a kiddie pool. I lived in Japan, by the way, for four years. Have you ever seen a koi who is over one hundred years old? I have. They are massive fish kept in massive ponds. The longest lived koi recorded was a female named Hanako. For her to live that long and that well, she did not live in a tiny, cramped space.
Bigwig, for proper koi care information, you will need to join a Koi forum. They will be able to better advise you on pond size, filtration, diet, etc. in order to properly keep the fish. You will not find much factual information here regarding their care.
Im sorry, but 250 gallons is not a tiny cramped space.
It absolutely is when a fish has a potential to grow to a meter in length. Some stellar individuals grow even larger than that. Any knowledgeable fish keeper would never recommend cramming such a fish into such a tiny living space, let alone having multiples in said space. If you could get away with such abhorrently small spaces for huge fish species, then Monster Fish Rescue wouldn't need to exist. Sadly, many people don't do their research on proper care, so neglect and improper care will never end.
Im not suggesting multiples. Im suggesting only one in this space.