Koi

Koi are omnivores that thrive on high-quality koi pellets as a staple diet, supplemented with fresh vegetables like lettuce, peas, and watermelon, as well as live or frozen foods such as earthworms and brine shrimp. Feed 2-3 times daily in warmer months, reducing frequency significantly as water temperatures drop below 10°C (50°F) since their metabolism slows considerably in cold water. Avoid overfeeding as uneaten food rapidly degrades water quality in their large enclosures.

Koi are active, social fish that do best when kept in groups of two or more, often schooling together and interacting with their keepers at feeding time. They are peaceful toward most tankmates but their large size and vigorous feeding behavior can inadvertently harm smaller fish. Koi are bottom and mid-water foragers that will dig through substrate searching for food, which can uproot plants and disturb the tank bottom.

Koi breeding typically occurs in late spring to early summer when water temperatures rise to around 18-20°C (65-68°F), with females scattering adhesive eggs among aquatic plants or spawning mops. A single female can produce hundreds of thousands of eggs, which hatch in 4-7 days depending on temperature. Raising fry requires separating them from adults who will readily consume the eggs and young, and culling is traditionally practiced to select the highest quality specimens.