Koi are one of the finest and most expensive ornamental fish for the garden pond. At the latest when the time for spawning has come, the males and females can be identified. Unfortunately, for certain reasons and without human help, the Koi offspring usually does not work as hoped. Creating optimal conditions and protective measures for successful propagation is not difficult at all.
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Laichzeit
When the temperatures constantly rise to over 20 degrees Celsius, the Nishikigois are often bustling with activity in the garden pond . As a rule, the so-called spawning game begins in June, sometimes as early as the end of May. The males (Milkner) are recognizable as these because they chase the female (Rogner). This means that the female, who has become plumper due to her eggs, swims in front, followed by the male. Their activity usually goes far beyond normal. They often jump out of the water like little dolphins and dive back in again. It is not uncommon for them to land sporadically on the edge of the bank and die there without help to get back into the water. If your koi jump around “happily”, it can be assumed that it is spawning time.
conditions
Only healthy koi that are given plenty of space and swim in water that is optimal for them will spawn, although not necessarily every year. It starts with high-quality koi food, which strengthens the animals and promotes organ functions. In addition, suitable places for spawning should be available. Otherwise, so-called spawning congestion could occur in the females, which usually has health consequences. The following water values also form the basis for successful propagation:
- pH between 7.5 and 8.5
- KH value over 5 °dH – carbonate hardness also stabilizes the pH value
- GH value over 5 °dH (total hardness)
- PO4 value less than 0.035 milligrams per liter (phosphate makes thread algae unusable)
- FE value less than 0.2 milligrams per liter (iron promotes plant health and consequently oxygen formation)
- Cu value below 0.14 milligrams per liter (too much makes koi sick)
- O2 value at least 8 milligrams per liter (without sufficient oxygen restrictions on egg formation, spawning and fertilization)
protective measures
To ensure that the koi do not injure themselves through their exuberant actions or even jump out of the pond, it is advisable to take appropriate protective measures:
- Stretch a net over the pond (also prevents birds from eating)
- Replace sharp-edged plant baskets that have become porous
- Refrain from cutting back under water on aquatic plants (sharp cuts could occur)
- Enlarge narrow passages at the edge of the pond so that koi cannot get stuck
- Angled spawning brushes in the shallow water area attract koi to spawn and reduce rummaging through “undergrowth”
spawning and fertilization
The koi go to the shallow water area to spawn. Here the males nudge the flanks of the females with their mouths to encourage them to spawn. A female can lay up to 1.5 million eggs. The eggs are usually fertilized by several males, provided they are present in the pond. Only between five and ten percent of the eggs have a chance of developing because, among other things, they irrevocably stick together into clumps immediately after the first contact with water and not every egg is accessible for fertilization.
detect spawning
Spawning usually occurs on the stems and leaves of aquatic plants and preferably on reed grasses that are found in the shallow water area. Here the so-called spawning cords can be seen after spawning. They are whitish-yellowish, the size of a pinhead and rounded in shape. In addition, there is usually an unpleasant odor caused by the fish sperm, which can become even more pronounced when the offspring leave the eggs and open spawns remain.
After spawning
When the koi have completed their egg-laying and fertilization, there is a general state of exhaustion among them. They behave conspicuously quietly to recover from the hardships. Now the time has come when the uninvolved koi and other fish as well as other pond and bank dwellers such as newts and frogs attack the eggs and eat them. Affected females and males will eat them lightly during the recovery period.
development
If there are still eggs after the pond inhabitants have satisfied their hunger, the offspring of the koi hatch after about three to four days. They sink to the bottom of the pond. If they survive there, the development proceeds as follows:
- First two to three days: consume protein and fats from their yolk sac
- Larvae: about five millimeters in size and transparent
- Then formation of swim bladder and pectoral fins – horizontal swimming possible
- Rise to the water surface
- Color pigmentation begins from the 3rd day
- From the 7th day formation of the rear fin – larvae between 12 and 14 millimeters in size
- Around the 13th day fin formation is complete – recognizable as small koi – can eat like adult fish
protective measures
In order to prevent the eggs from being eaten after spawning and to significantly increase the chances of successful reproduction, the eggs and later larvae of the koi should develop outside the garden pond in a certain protected area. The respective instructions explain what koi lovers need and how to proceed:
Materials/Utensils
- aquarium or tub
- Malachite green oxalate (to prevent various diseases and especially against fungus in koi eggs)
- Water/aquarium heater
- Aeration/oxygen pump
- Special seed food
- According to experience, a mixture of
- Boil the egg yolk, mix it with pond water and let it run into the pool
- Freshly hatched or frozen brine shrimp (Artemia salina) (feed crushed)
- Koi food from the specialist trade
Implementation instructions:
spawn brush Fill the container with pond water
- Add malachite green oxalate and mix well
- Insert pump
- Check the pond/aquatic plants for eggs, remove them and put them in the tank
- If the spawning brush was used, remove it and place it in the water basin
- Turn on the heating and set it to 20 to 22 degrees Celsius (if the temperature falls below 5 degrees Celsius, the eggs die)
Cultivation instructions:
- Carefully remove the spawning substrate after hatching (deteriorates the water quality due to pollution)
- The larvae swim and start feeding
- Feed five to seven times a day in water temperatures between 20 and 22 degrees Celsius
- Check the water values daily, especially for ammonium and nitrite (allow the offspring to die off quickly)
- Regular water changes – pond water is still ideal (ensure the right temperature)
- After four weeks, discard undersized and/or crippled fish
- Changed diet to koi food, but grind beforehand
- After about three months, feed koi food in small pellets
- From a size of five to seven centimeters, the young fish can be released into the garden pond
