Primary consumers are organisms that feed directly on plants or other producers. In aquatic ecosystems, primary consumers are typically herbivorous fish, invertebrates, and some species of zooplankton. Angelfish are a type of freshwater fish that primarily feed on algae, small invertebrates, and zooplankton. As they consume these organisms, angelfish play a crucial role in the transfer of energy from producers to higher trophic levels within the aquatic ecosystem.