ive bought this before for my fish and it worked pretty well. if its cold outside when you try to feed them this food they dont eat much, And next time flip your picture =]

My guess would be that even different animals of the same species can like different things. Pond sticks of approximately the same nature (based on the far left of your picture) have kept some of my fancy goldfish (members of the carp species, like your koi) happy for well over a decade, and have kept my pond well populated for two of them. If you're going to try something different, don't try a different stick. Try a flake, or a slow-release pellet, then see how they react. Being bottom-feeders, and conditioned to a certain feeding program in whatever pet store you most likely got them from, they certainly aren't genetically inclined to being fed from above in any manner, and may have been conditioned to expect a different type of food than you're offering them. Find a similar food with a different delivery mechanism, and try that.

that particular kind is really for regular pond goldfish like comets. They carry one that is specifically for koi. it's in a light purple box. Same company though.