This sounds really weird to me? How long have you had your ADF? I have been keeping ADFs for over 12 years now and I have never had a problem with them being agressive towards other fish. Is it possible that you were sold an african clawed frog under the name of ADF? I have seen it happen in many fish stores. The 3 ADFs that I have right now will eat flake, freeze-dried food, algae wafers. I have seen them eat off of the bottom as well. In all the years that I have had them I have never had to feed them live food, and they all have lived for years.
T/A- Are they not eating, or have you not seen them eat? What happens to the food that you put in there for them? Do you have to take it out after awhile? I didn't see my frogs eat much either, but like jd_energy says, they must because they are still alive. When I see them at the surface sometimes I drop some freeze-dried bloodworms in there and they go wild.