One great koi joys I had last year was mixing up Izeki paste by the bowl and hand feeding the fish. Wish I could get Izeki paste this year.
I'd hold a nice big chunk in my closed fish and hold my hand about a foot under the water. The fish would see what I had and ATTACK! The attack is why I used a fist; they would try to take off with a finger if one was sticking out.
I could also make sure everybody got their fair share -- if a couple fish were hogging the food I could just move my hand over to some fish that were left out. And after a bowl most of the fish were happily munching their chunk of food so some of the more shy fish could then be tossed a couple of chunks.