Koi and Goldfish Food
The type of food you feed your Koi and goldfish, coupled with the quantity you offer them at each feeding, has a major impact on their health and growth. Portion control is king. Feed your Koi just enough food for a 5 minute feeding session. Choose a size that is small enough to be eaten by the smallest fish in the pond, otherwise they may die of starvation. Koi will eat almost anything; avoid feeding them with foods that deliver bulk but are lacking in nutrition. Below is advice from Kodama Koi Farms:
DIET IS KEY
"Feeding your koi is such a fun peaceful activity for the whole family, watching your beautiful koi gather and parade in front of you. It is tempting to feed more often to enjoy this experience, especially when guests of children are around. But it is very, very important to NEVER overfeed!
Any leftover food will sink to the bottom and decompose, creating a dirtier environment, throwing your nitrogen balance out of whack and using up your koi’s oxygen supply. Overfeeding also makes it hard to discern if fish are sick or just full. Twice a day, feed them only as much as they will vigorously eat for one minute. Keep an eye out for if there is leftover food, and adjust your feeding accordingly."