Need help feeding finicky marine fish?

My blue hippo and imperator angel don't eat the conventional way (you throw food in the tank they come and devour it). Instead, they hide when i approach the tank and if i throw the food, the food will just float and sink to the bottom and foul the water. I found a workaround by putting a whole piece of Formula 2 frozen in a piece of net on a clip, then my hippo will come once in a while and pick at it then move away, come back pick some more, then move away. This goes one for hours until the whole cube is gone. However, the angel food does not stay whole, neither do 90% of the fish foods, they just float into pieces, so i can't play the same trick with the angel. what do i do? he picks at the algae strips on the clip, but i want to also feed him the proper angel foods. Please help