If i put my Red ear slider with my guppy will my RES turtle eat the fish food?

Okay so im getting the food today cause i just bought 4 guppies my turtle has ate none of them for now i put lots of hiding places for the guppies. The turtle didnt even look at them i know one day theyll be eaten but for now they look safe. should i have any cautions and is there anyother type of fish tht can eat the waste in the tank or something.??