African Dwarf Frogs are not scavengers so don't rely on them eating what is "leftover" from your other fish. They will eat most any sinking food, mine eat shrimp pellets, frozen bloodworm (their favorite), frozen mysis shrimp, flakes that make it to the bottom, and tropical fish pellets (Bio Blend by Marineland). As a treat (mostly when I feel like dealing with stinky live foods) they get live blackworms as well. Mine obviously are not picky, but then most of them are not anyhow.
\Dan