Koi fish do eat other fish, and this is mainly related to their feeding habits and behavioral characteristics. Here is a detailed analysis:
Feeding Habits
Adult koi are omnivorous. In addition to plant-based food, they also prey on small fish, crustaceans, and more. When food is scarce, they may even nibble on grass goldfish or goldfish.
Behavioral Reasons
Territory Competition: Koi have a sense of territory and will attack other fish that enter their activity range.
Breeding Protection: Male koi become more aggressive during the breeding season and will bite other fish to protect their mates and spawning grounds.
Defense or Play: Sometimes, nibbling behavior may stem from self-defense or curiosity.
Suggestions for Mixed Breeding
When keeping koi with their own kind, they usually do not attack each other. However, attention should be paid to differences in body size to avoid food snatching.
Mixing koi with other fish species requires caution. It is necessary to ensure an adequate food supply and provide sufficient space.
It should be noted that excessive nibbling may cause injury or even death to other fish, so close observation is essential during breeding.