Koi are omnivores by nature and will eat just about anything in the wild, including algae, plants, and insects. When keeping koi as pets, it’s important to keep their natural diet in mind.
They need a balanced mix of proteins and plants to get the right combination of vitamins and minerals they need to grow, stay healthy, and develop vibrant colors.
What you feed your koi is just as important as what you don’t. Here’s what you should feed them and what you should avoid to prevent any problems in the future.
What Kind of Food to Feed Koi Fish?
Before we get into specifics about what food koi should eat, there’s something else to consider: whether the food sinks or floats.
Each has pros and cons that should be considered before deciding which is best for your fish.
Most koi food available in pet stores is the floating type. It’s commonly used by hobbyists and is readily available. One reason that this food is so popular is that you can watch the fish as they eat, which is one of the most fun parts of keeping koi.
Another great thing about floating koi food is it lets you get a good look at your fish on a regular basis. This makes it really easy to do health checks and gives you a chance to get to know their behavior a little better so it’s easier to determine if something is wrong.
Koi have to come to the surface to eat floating food which gives you an opportunity to visibly check for any injuries and make sure all of your fish are eating. If you spot one that doesn’t have an appetite, it’s much easier to observe them for illness or injury this way.
The downside of floating food is that it can quickly get pulled into the filter or skimmer before your koi get to eat it. If this becomes a problem, you can always turn the pump off during feeding or use a floating feeder.
The best thing about sinking food is that koi are better at eating food that’s fallen to the bottom of the pond. Their mouths actually face downward and, in nature, they eat worms and other things they find in the mud.
Because this is their preferred way of eating, it’s much more efficient and can have better results. There’s a lot less waste which means that you don’t have to use as much food and there isn’t as much left behind to affect the chemical balance of the water.
The downside, of course, if you don’t get to watch them eat which makes it more difficult to monitor their health and behavior. It’s easy to overlook injuries or miss identifying a fish that isn’t eating well.
What Kind of Food
Koi need a wide variety of nutrients to thrive. The following are the ingredients to look for when choosing food for your koi:
1. Spirulina algae
This blue-green algae naturally grows in hard water with high pH. It’s small and floats freely rather than growing on rocks of branches like other types of algae so it’s easy for koi to get to.
There are a lot of benefits for koi that eat spirulina algae. It improves digestion which helps prevent bloating, boosts the immune system, and results in a higher growth rate.
2. Wheat germ
The germ is essentially the seed of the wheat plant. Wheat germ helps koi grow faster and provides a healthy amount of vitamin E which has a lot of benefits, including improved oxygenation and circulation and a healthy immune system.
Koi need more wheat germ in the cooler months when their metabolism starts to slow down. The fat in wheat germ is easy to digest when and helps them prepare for hibernation.
3. Brine shrimp
We mentioned that koi are omnivores so it’s important that they get enough protein in their diet. Brine shrimp are a great choice because they’re rich in other important nutrients as well.
Brine shrimp is a great choice during periods of high activity. For example, freshly hatched koi need extra protein to fuel growth and adult koi need it in the summer when their metabolism gets faster and they’re very active.
Just like any pet, koi like treats. Some of their favorite snacks are watermelon, orange slices, broccoli, lettuce, garlic, shrimp, and worms. Keep in mind that these things should only be given as a special treat and in moderation.
What Not to Feed Koi Fish?
Stay away from low-quality koi food because it won’t have the delicate balance of vitamins, minerals, and nutrients that koi need to grow strong and healthy.
You should also avoid giving koi anything that’s very high in carbohydrates like peas, bread, or corn. Not only are these foods hard to digest, but they can also cause health problems if eaten in excess.
When is the Best Time to Feed Koi Fish?
Because most people keep koi in an outdoor pond, the temperature is a huge factor in when to feed them.
Like a lot of fish, koi are cold-blooded. The temperature of their environment directly affects their metabolism. So, their feeding schedule actually depends on the season and the type of climate you live in.
Koi eat very little or not at all when the temperature falls below 48 degrees F. It’s actually best not to try to feed them when the temperature is this cold because there’s a good chance they won’t eat. The food will rot and contaminate the water.
Believe it or not, the temperature also determines what type of food they should eat in order to facilitate easy digestion. For example, when it’s between 48 and 64 degrees F, the fatty foot is best, especially foods that contain wheat germ.
When the temperature rises above 64 degrees F, koi need more protein, though you should still mix it up with some vegetables and fruit.
Monitor water temperature in the summer months. If it goes higher than 88 degrees F, you really have to monitor feedings and the water chemistry. Temperatures this hot can be stressful for your koi.
When the water gets too hot, it loses some of its ability to carry oxygen, which makes it harder for koi to breathe. To compensate, they breathe faster which increases the ammonia in the water.
You should still feed your koi in the summer but try smaller meals more frequently when it’s at or above 88 degrees F. And pay close attention to the water chemistry.
How Often Should You Feed Koi Fish?
How often you should feed koi also depends on the season.
You might be tempted to start feeding your fish as soon as the coldest winter days have passed but you should never feed them when the temperature is below 48 degrees F. As temperatures start to warm, their metabolism speeds up and they’ll soon be ready to eat.
Start with one feeding per day until they become more active. As it gets warmer, they’ll get more and more active at which point you should feed them twice a day.
In the summer, koi get hungrier the higher the temperature gets. For temperatures between 73 and 77 degrees F, you should feed them four times a day. When it gets above 77 degrees F, feed them five times a day.
As we mentioned, when the temperature approaches 90 degrees F, it’s better to do smaller, more frequent feedings and remember to keep a close eye on water parameters.
As it moves toward fall and the temperature starts to cool, koi become less active and need less food. They’ll swim slowly and lose their interest in eating. Gradually transition from high protein summer foods to high-fat foods during this time.
When it falls below 64 degrees F, begin feeding your koi no more than twice a day. When it gets below 48 degrees, stop feeding them for the winter.
How Much to Feed Koi Fish?
How much food you should give to your koi depends on how many fish you have in your pond and what time of the year it is. To figure out what your koi need, follow the Five Minute Rule. Give your fish as much food as they can eat in five minutes.
After five minutes, any food in the water must be removed. Scoop up what’s left behind and give them a little less with the next feeding.
It’s important to get this balance right but remember that it’s always better to underfeed than overfeeding. Underfeeding can stunt their growth over time but overfeed causes a lot of issues, including accumulation of waste, bacteria, and algae in the water. This all leads to oxygen loss and unhealthy fish.
Koi require high protein foods for energy in the summer when their metabolism is fast and they’re very active. They should eat four or five times a day following the five-minute rule. As the temperature drops, feed them less and less. Below 48 degrees F, stop feeding them for the winter.
Remember, when the temperature approaches 90 degrees F, feed them less food more often and monitor the water parameters carefully. When it gets that hot, less oxygen is available in the water and ammonia levels rise.
There are a lot of things to consider when feeding koi. What you feed them is as important as when and how much.