Disclaimer...I have not done this myself, but I read about it years ago and it seemed easy and effective.
Mount a wire basket on a pole that is placed in your pond, perhaps even off of a dock. Throw unwanted fish and leftovers from cleaned fish in the basket. As they break down, the "fish parts" will drop through the basket into the water below...where the surviving fishies will get the morsels.
The basket needs to be stout enough to keep the raccoons and birds out mainly.
Somewhat similarly...I once was at a pond where the owner had set up a peculiar "fish feeding station".
He would pick up roadkill, raccoons mainly, and then using a stiff piece of wire run through their hind leg and attached to a dock, he would toss the roadkill out in the pond. The coons would float while they rotted and the flies would get to the top, exposed, part of the coon, lay eggs that would turn to maggots. Birds would peck the rotting carcasses and the maggots would fall into the water where the giant bluegills would eat them. Circle of life!
