Yonsai Japanese Koi are typically around four years old, meaning they’re more mature, larger fish with fully developing body shape and colour pattern. At this stage they are confident, active pond inhabitants and generally peaceful, but their size and activity mean they’re best suited to established ponds with strong filtration and good swimming space. A minimum pond volume of around 4,000–5,000 litres with excellent water quality, high oxygen levels and stable temperatures is recommended. Yonsai koi thrive in well-maintained ponds with gentle to moderate flow, plenty of open water to cruise in, and should be kept with other similarly sized koi to avoid stress or bullying.
