Pond Koi Tips Tricks Food

My koi have always liked or not liked food spiting it out I have used all different foods trying to find one they all like and now it seems I have.
I cannot understand how some fish like some food and others a different food.
One point to remember is most Koi food is made by one company in China then packed in the UK under what ever name is on the container or bag.
Shape plays apart as well I have purchased pellets size 3 and 6 of the same food and its remained floating on the pond.
So, they like the sticks in this but not the pellets.
Anyway, a new food due today so I will try that and post what happens.