This may seem like a really dumb question to lots of you, but I am learning. How do you feed your fish when the overflow sucks everything up in a very short time? Do you turn it off each time?
I use a turkey baster and only let out as much as the fish will eat before it goes all over the tank. You kindof have to stay away from floating food. Unless you want to turn your pump off.
Another thing, they may help, is to put the flakes or whatever in the water instead of "sprinkeling" them on top of the water leaving them to float into the overflow
For flakes I like to pinch them between my two fingers and have the fish come up and eat it out of your fingers. It takes a while to get your fish trained to do it, but they will. It feels weird when they are all biteing your fingers.
When I am in a hurry, but I know I need to get something dry like flakes in the tank. I will add them to the surface and then stir the top of the water real quick and the flakes mix in to the water so they don't all go down the overflow.