Koi are large domesticated carp commonly kept in backyard ponds. Some koi are exceptional specimens, called “show koi” and can be very expensive. Many pondkeepers keep less expensive pet koi; they may not have perfect colors and markings, but they are great pets. There are many koi varieties available to the koikeeper, including Asagi, Bekko, Doitsu, Kohaku, Sanke, Showa, Tancho and Utsuri, and they all make great pets. When stocking the koi pond, make sure to provide at least 100 to 200 gallons per adult koi fish. Larger jumbo koi should be in larger ponds that have 1,000 gallons per koi.
Koi fish are omnivorous and eat food off of the bottom of the pond. Their barbels help them locate worms, algae and other foods in or on the substrate. Choose a koi pellet food that corresponds to your fish’s size (smaller koi should be fed smaller pellets). Feed more protein during the summer than during the winter. In the summer, provide up to 36 percent protein; in cooler temperatures, when your fish’s metabolisms have slowed down, feed 25 percent protein. When temperatures drop below 50, stop feeding for the rest of the winter. There are many kinds of foods you can feed your koi, even ones with added vitamins or color enhancers. You can also feed treats once a week or so during spring and summer. Good treats include Romaine lettuce, oranges, earthworms, ghost shrimp, etc. Make sure to follow the feeding instructions on the food package so you don’t overfeed your koi.
Breeding: Your koi may breed in your pond during the breeding season (after temperatures reach 68 degrees, usually February through May, depending on the area), but if you want to deliberately breed your koi, you should prepare a breeding setup. Set up a 200-plus-gallon container with a filter, air pump, heater, a cover and spawning mops or plants. Select a healthy female and condition her in the breeding setup for several weeks by feeding her well. Once she’s filled up with eggs, add the male, and in about 12 hours, the breeders will lay and fertilize 2,000 to 50,000 eggs. Put the male back into the pond and put the female into a hospital aquarium to recuperate after the strenuous event. Good breeders will be healthy adults that have the characteristics you want to pass on. Females should be 3 to 8 years old, and males should be 3 or older. Males have raised bumps called tubercles on the head and pectoral fins during the breeding season. Females are lacking these pumps, and they have smaller, more rounded pectoral fins.
After the parent fish are removed from the aquarium, do a water change and make sure there is a good current in the container (so the eggs don’t develop fungus and die). In six days, the eggs should hatch. They first need to be fed liquid fry food, and once they’re large enough, feed them larger foods, including crushed commercial foods, baby brine shrimp, Daphnia, etc. At three months, they should be able to eat adult foods. Because there are so many fish from one spawn, you will need to cull 60 to 80 percent of your baby koi once a month. First cull the sick, deformed or small fish. Once they begin to develop color, cull those that have undesirable traits for the koi variety you are breeding. Keep in mind that koi change colors for several years while they are young, so their colors will not stay the same.