Koi fish, as an ornamental fish, should purposefully choose its parent fish for breeding. Koi fish mainly looks at the back, so it's best to choose the parent fish with flat up and down, flat oval cross-section and overall rotating shape, and the color should be selected according to the breeding purpose.

Step 2 prepare the spawning pool

Small cement ponds are generally used as spawning ponds. The shape of the pool is not limited, and the scale is 4 meters high, 4 meters wide, 0.8 meters deep and 0.4 to 0.5 meters deep. The PH value of aquaculture water is 7.2-7.4, and it is better to use slightly salty and low-hardness water, and the dissolved oxygen in the water should be above 4 mg/L. Pay attention to the disinfection of the pond and put the fish nest prepared in advance into the pond. Fish nests are generally Myriophyllum or palm skins soaked in water and tied into small bundles.

Step 3 lay eggs

In northern China, late April to mid-June is the breeding season of koi fish. When the water temperature rises to 16- 18℃, the selected parent fish can be moved into the spawning pond, and only 2 13 groups of parent fish can be put into each pond. After the parent fish enter the pond, when they are found chasing each other, it means that they are about to lay eggs. Generally, spawning begins around 4 am and ends around 10. Generally, it can lay 200,000-400,000 eggs at a time.

The egg diameter in koi fish is generally 2. 1 to 2.6 mm. After the egg is laid, it absorbs water and expands, and the egg membrane is pulled out, so it will stick to the fish nest and hatch. After the parent fish lays eggs, the fish nest containing fertilized eggs is taken out and eaten with 5%-7% food.

Soak in salt water for 5 minutes for disinfection, then take out the new fish and hatch in the spawning pool.

Step 4 hatch

The water depth during hatching is generally 30 cm, and the requirements for water quality and temperature are the same as those during spawning. Incubation time is directly related to water temperature, which is shortened with the increase of water temperature in a suitable range, and it is 4-5 days at water temperature 18℃, 3-4 days at 20℃-22℃ and 3 days at 25℃. The newly hatched larvae don't move or eat, but get nutrition by absorbing the yolk sac in the abdomen. After the yolk is absorbed, the larvae begin to swim freely and open their mouths to eat outside food. At this time, bait should be cast in time.

5. fry cultivation

The breeding process of fry is also a process of survival of the fittest, and it is a process of multiple selection and breeding. The selection process is usually carried out 3-4 times within 3 months after the larvae hatch.

The first selection: it will be carried out within 20-30 days after the larvae hatch, starting when the fish is about 3 cm long. It is mainly to select and retain individuals with strong physique, lively swimming and obvious variety characteristics, and eliminate other individuals or cultivate them separately for sale. However, due to different varieties, their growth speed and the time of forming stripes are also different. For example, the selection of Showa tricolor koi fish begins about15th day after hatching, golden koi fish begins about 50 days after hatching, and red, white, big and true tricolor koi fish begins about 60 days after hatching.

Second selection: The first selection will start in about 20 days. The selection criteria are thin appearance, bright color, clear pattern and markings, obvious variety characteristics and so on. After that, the third and fourth choices are basically the same as the second choice.

First, how to choose koi fish

Koi fish's choice can be based on certain criteria. Since ancient times, the evaluation standard for koi fish has been the system of 50 points for posture, 30 points for color and 20 points for pattern, totaling 100 tribute. Recently developed into a 30-point gesture.

Color 20 points, pattern 20 points, quality 10 points, grade 10 points, style 3-2-2-1. Among them,

Posture includes swimming stroke and body shape, and genetic factors are dominant; Moreover, the color and pattern should be beautiful, with its own quality accounting for 70%, water quality accounting for 20% and feed accounting for 10%. Therefore, improving water quality is particularly important for koi fish. The so-called excellent water quality means that the pH value is between 7.2 and 7.4, and there are few iron ions, chloride ions and sulfate ions, low hardness and rich dissolved oxygen. At the same time, the feed is rich in colored substances such as spirulina, Antarctic krill, alfalfa meal, shrimp, shrimp skin or artificial pigment.

Second, how to identify the male and female of koi fish?

The abdomen of female fish is bigger than that of male fish; The anus of female fish is wide and flat, nearly round, while that of male fish is small and oval; In the stage of sexual maturity, the lateral fin of male pectoral fin has rough horniness "idolization".