I have a 55 gallon tank with 22 fish. Tetras, danios and corys. I mostly use flake food which I pinch to make it smaller. The concern is most of the food is eaten by the danios and tetras at the surface leaving little for the black phantom tetras which tend to stay near the bottom half of the aquarium with the corys. I dont want ot overfeed but how do I get more food to the bottom?