What do turtles eat in a pond?

I had a turtle and i spent about 100 $ on him in one visit of the pet store. I got him water falls grass plants, you name it. And soon enough I found out that turtles love to dig or burro. His whole habitat was destroyed. Into wreckage that you couldn't believe a turtle not even 6 in. long could do. so i wouldn't recommend too nice of a habitat.