Well, carp are omnivores, so they're not only bottom feeders.
I've seen em in lakes eating stuff that floats like seeds and berries from trees and bushes, or if you're in city park lakes or Laughlin, stuff like Nacho Cheese Doritos, popcorn, Cheetos, that fake
chicharrón that the street vendors sell, and so forth.
In areas where there are insects still left, they will also eat those that are floating, like hoppers, ants, beetles, bees...
But unless they're actively feeding on top, don't waste your time. Instead, fly line some masa on a small mosquito hook on 4 pound test, set your drag correctly, buy a raspado or a paleta, and hang on.