Koi Spawning Season: Tips on Care, Pond Management & Spawning Brushes

The spawning season for koi carp usually begins in late spring, as soon as the water temperature is a constant 18 to 22 degrees Celsius and it is light for longer. In Central European ponds, this is usually the case in May or June. However, the exact time can vary depending on the region and weather conditions. It is important that the water remains warm for several days in a row.

When the female is ready to spawn, the male begins to drive the female: He pursues the female, nudges her on the belly and drives her to lay her eggs. This behavior is often very hectic and can lead to wild scenes in the pond. The eggs are then laid on plants or other substrates, such as spawning brushes, in the water and fertilized directly by the male.

Intensive reproduction is associated with high stress and the risk of injury. Females in particular are often forced into shallow bank areas where they can injure themselves on stones or sharp-edged objects. Make sure that your pond is safe for spawning and remove any sharp edges or obstacles.

A proven method for controlling egg deposition is the use of spawning brushes. These are brush-like substrates made of soft plastic fibers that are fixed in the water. They provide an optimal surface for the eggs and simulate natural spawning grounds.

• Koi specifically lay their eggs there

• Easier control of reproduction

• Removal of possible excess eggs

• Avoidance of heavy water pollution from fungal, unfertilized eggs

After spawning, the brushes can be removed and cleaned or transferred to a separate tank for targeted breeding.

The fish are very stressed after spawning. The water is heavily polluted. Immediate feeding further stresses the water and the fish. Wait at least five to seven days before feeding for the first time.

The water quality can deteriorate drastically after spawning. Pay particular attention to:

• Ammonium/ammonia (NH4/NH3)
• Nitrite (NO2)
• oxygen content
• pH value

Spawning residues and organic material often lead to short-term peaks in pollutants (ammonium/nitrite).

Carry out several water changes of 20% over the following days. This is often accompanied by foam caused by all the protein in the water. Depending on the amount, the water may also smell bad.

A slight salting of the pond to 0.1% (1 kg salt per 1'000 liters) can help to reduce the stress level of the fish. The salt stabilizes the mucous membrane and supports the regeneration of small wounds. Be sure to use iodine-free salt.

Typical symptoms after the spawning season:

• Red spots or abrasions on the flanks
• Apathetic behavior
• Rubbing on pond walls

Minor injuries usually heal on their own. In the case of conspicuous changes, e.g. protruding and inflamed scales, removal and treatment with antiseptics may be necessary.

If you are not planning any targeted breeding and know what to do with the many small koi, it is advisable to remove the eggs. Spawning brushes are an advantage here as they can be easily removed. If they remain in the pond, many unfertilized eggs will turn fungus and can worsen the water values. Some fry will still survive, but are often eaten by the adults.

From May and June, at water temperatures of 18 to 22 °C and when the days get longer.

It reduces stress and supports the healing of minor injuries. It also masks high nitrite concentrations.

Spawning brushes are artificial substrates for laying eggs. They are hung in the pond for a few days and can then be removed together with the eggs.

No, wait at least five to seven days depending on the water quality.

The spawning season for koi carp is a natural but challenging event. With the right preparation - from setting up spawning brushes to targeted pond management afterwards - you can help your fish to survive this phase in good health. Pay attention to the water values, add salt if necessary and keep a close eye on your animals. This will lay the foundation for a healthy koi population and perhaps also for your first own offspring in the pond.