This hopper will direct the fish food down into the aquarium and keep it within the floating ring.

Print the floater and seal it completely using clear poly and it will float to the height of your water level and keep the food inside the ring. You can tap the two holes for 1/4-20 and get plastic thumb screws to mount this to your tank. The Apex feeder and several other commercialy available auto fish feeders will work with this hopper.