What do koi eat?
Koi are fed mainly on a formulated pellet food made for pond fish, with the type and amount changing through the year as water temperature affects how well they digest. A higher-protein growth food suits the warmer months, while a lower-protein, easily digested food is more appropriate as the water cools, alongside the occasional fresh extra like peas or lettuce.
Why the diet changes with the seasons
A koi's metabolism slows down as pond water cools, and their ability to digest protein efficiently drops with it. Feeding a rich, high-protein food during cold weather can leave undigested food sitting in a sluggish gut, which is more likely to cause harm than good.
In the warmer months, when koi are active and growing, a higher-protein pellet supports that growth properly. As the water cools into autumn, switching to a lower-protein, wheatgerm-based food that is easier to digest suits their slowing metabolism, and feeding generally stops or drops right back once the water gets genuinely cold.
How much and how often
A good general rule is to offer only what the koi will finish within a few minutes, rather than a fixed amount by weight. Uneaten food breaks down in the water and affects water quality, which matters more for koi health day to day than any single meal.
Several small feeds through the day tend to suit koi better than one large one, particularly during the warmer months when they are actively feeding. During colder weather, feeding drops right back, sometimes to nothing at all once the water is cold enough that they stop feeding naturally.
Fresh extras, in moderation
Cooked peas with the skin removed, and small amounts of washed lettuce, are commonly offered as an occasional extra alongside a proper pellet diet. These should stay a small supplement rather than a replacement for a formulated food, which covers what koi actually need nutritionally.
If your koi go off their food, show unusual colouration, or seem lethargic, that is worth investigating rather than assuming it will pass — a vet with fish or aquatic experience, or a specialist, is the right person to speak to if something seems genuinely wrong.
What these need
Things we stock that owners commonly reach for here. Nothing on this page depends on you buying one.
Tetra Pond Fish Food Pellets
Complete floating Tetra pond pellets for pond fish, offered in two pellet formats
£9.22
Tetra Pond Fish Food Sticks
Complete fast-soaking Tetra Pond Sticks for pond fish, in seven pack sizes
From£4.77
Tetra Gold Japan
Sinking dry pellets for fancy goldfish, with pack-specific label information shown clearly
From£4.56
Tetramin
Complete TetraMin flake food for ornamental fish, offered across several pack sizes
From£2.39
Common questions
- Can koi eat bread?
- It is best avoided. Bread offers little nutritional value, can affect water quality as it breaks down, and swells in a way that is not ideal for a koi's digestion. A proper pond fish pellet is a far better everyday choice.
- How often should koi be fed in winter?
- Very little, or not at all, once the water gets genuinely cold. Koi's metabolism slows dramatically in cold water, and feeding a fish that is not properly digesting can do more harm than simply letting them fast through the coldest months.
- Do koi need a different food to goldfish?
- Koi and goldfish have broadly similar dietary needs, and many pond foods suit both, though koi often benefit from a food specifically formulated for their size and seasonal feeding pattern. Checking the label for what species it is intended for is worth doing.
- How do I know if I'm overfeeding my koi?
- Uneaten food left sitting in the pond after a few minutes is the clearest sign. Overfeeding affects water quality over time, which is often a bigger risk to koi health than the food itself, so feeding only what is eaten quickly is the safer habit.
Related
Sources
Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.
Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.