The protein content in food pellets should be at least 30 percent. Protein content in pellets varies greatly depending on manufacturer—usually between 25 and 36 percent—so read labels before deciding. The primary source of protein should be fish meal or soybean meal. The fat content (from fish oil) in the pellets should be at least 5 percent. [2] X Research source

This step is especially important when the feeding frequency is low or fish are especially hungry, otherwise, they may consume the pellets too quickly and end up eating dry pellets. Dry food can expand in the digestive track, increasing the risk for life-threatening internal blockages. [4] X Research source

Natural pond plants include ordinary pond algae, as well as other plants like duckweed. Vegetable scraps like peas, carrots, spinach, leaf lettuce, and so on, are also a good choice for supplementation. [5] X Research source

Some people also provide scraps from fish they have prepared for their own meals as an occasional dietary supplement. [6] X Research source

Look for foods that contain spirulina, shrimp, or krill. In the wild, koi eat crayfish, which are high in carotenoids, an important nutrient for enhancing the color red. [7] X Research source

Feed koi crustaceans, insect larvae, worms, and aquatic plants. Also include live plants to give koi some roughage and added vitamins and minerals.

Domestic koi generally grow to 12 to 15 inches (30. 5 to 38. 1 cm) long. [9] X Research source Most koi reach 50 percent of their final adult length in 24 months, 95 percent at 10 years, and 99 percent at 14 years. Update your notes at least twice a year to ensure your calculations are accurate.

The most accurate way is to actually weigh your fish, although this isn’t always practical. Charts can also help you determine its weight. Most give an estimate using the fish’s length and build. For example, typically, a 12-inch long koi weighs around 12 ounces.

When water is between 60 to 85 °F (15. 6 to 29. 4 °C), feed your koi two to four times per day. When the temperature lowers to 50 to 60 °F (10 to 16 °C), feed them once a day or every other day. Monitor the temperature year round. If the temperature rises above 90 or below 50 °F (10 °C), it is best to stop feeding your koi as their metabolism will slow and they will not be able to properly digest their food. Koi will still have access to food in those cases where the water temperature is too high or too low. They will be able to eat the algae on the pond liner or rocks.

For example, a one-year-old fish living in 72 degree Fahrenheit water needs to eat two percent of its body weight in food each day. A four-year-old koi needs one percent. Take this percentage times the weight of the fish to determine how many grams of food it needs each day. [10] X Research source

For example, say you have a one-year-old fish that is five inches long and weighs 22 grams, living in 72 degree Fahrenheit water. According to your chart, it needs to eat two percent of its body weight per day. Your calculations would look like this: (5 in. ) x (0. 02 x 22 grams) = 0. 44 grams per day

For example, say you have a one-year-old koi and a four-year-old koi in your pond. The one-year-old koi is five inches long and weighs 22 grams. The four-year-old koi is ten inches long and weighs 200 grams. The water temperature is 72 °F (22. 2 °C). Based on age, weight, and water temperature, your one-year-old should receive two percent of their body weight as food per day and the four-year-old should receive one percent. Using the calculations from the previous step, the one-year-old needs 0. 44 grams of food per day. The four-year-old needs 2 grams per day [(10 in. ) x (0. 01 x 200 grams) = 2 grams per day]. Add 0. 44 and 2 together to get the total grams you need for both of your fish each day (2. 44 grams). [11] X Research source

You want your koi to be able to eat all of the food you give them in a short amount of time (less than five minutes). Overfeeding koi can cause serious health problems like severe negative impacts on the liver and other internal functions. Pre-portion your fish food to keep from overfeeding. [12] X Research source

This will help you increase the bond between you and your fish. Once you have established a strong bond, you can work on hand-feeding your koi.