Just started feeding floating pellets, my fish don't realize they are there and don't eat them

I have a new fish pond and inherited bulk fish flakes and had been feeding those, the fish would eat them while they sank and occasionally grabbed the floating ones. I've switched to pellets that float and the koi and goldfish just don't realize they are there and don't eat. I have been feeding both pellets and flakes just so they have food and hopefully learn overtime. How do you encourage them to know there is food, and how long does it take for them to learn?