There is another potential problem with trying to fill all of the niches. If you increase the biomass you might reduce the amount of DO available to all species and also increase the amount of manure to be absorbed by the water. My Farmer Grandfather once told me to "Think Like the Soil". In the case of a pond, I think you have to take a Holistic outlook and imagine yourself as the water in the pond. I remember Bill Cody once posting here to an owner of a large aquarium. He said "The fish are swimming in their own toilet" or something to that effect. I believe a pond is the same thing. Think of the water before you overstock or even fertilize to increase the carrying capacity.