I hand feed Optimal, so I'm able to closely observe what the fish are reacting to the pellets.
If the behavior in my pond is even slightly typical, I'd say you have little to worry about in terms of pellets making it to the bottom of the pond.
BG will readily take a pellet as it sinks, RES prefer a sinking pellet, and will pick them up off the bottom with gusto.
Assuming that you are throwing a reasonable amount, into water with a bit of depth, it's not likely that many pellets are being wasted.
