A well designed koi pond will remove solids (sinking or floating) fairly quickly. Now Don points out one way of controling the amount of food to get into the skimmer. the same method would work for the bottom drain by having that system's pump on a remote. Personally, my bottom drain system is pulling from 360 degrees (as most do) and will remove sinking solids much faster than a skimmer located on one end of the pond. By feeding floating pellets in an area where it takes the longest to get to the skimmer, I minimize any wasted pellets where as sinking pellets end up in my filters much faster. I guess that is 1 drawback of an efficient system design.
I'll stick to my floating pellets.
Steve