Enemies of Phytoplanktons in Aquatic Environment
PhytoPlanktons are “plants”. They are evolved after microbes. The next higher organisms are ZooPlanktons. “Zoo” means animals and thus “ZooPlanktons are higher than PhytoPlanktons in the evolution hierarchy. It is but natural that ZooPlanktons eat PhytoPlanktons and thus the natural food of Aquatic Animals have a predator in the pond environment.

Thus, ZooPlanktons are enemies of PhytoPlanktons and therefore survival of natural aquatic animals depend on how the Pond Environment is favourable for growth of PhytoPlanktons so that even if some population of them get consumed by ZooPlanktons, their populations must be adequate enough to feed the Aquatic Life.