They provide coverage of the water to keep out the sunlight. Aquatic plants will provide a safe haven for fish and frogs to lay their eggs, as well as providing oxygen and food for them. They also absorb excess nutrients and other forms of water pollution and algae growth. Plant aquatic plants in no-hole plastic containers to minimize maintenance. A soil that you would use for growing vegetables will work well.
Most aquatics require at least five hours of direct sunlight for optimum growth.
The University of Florida has a complete computerized bibliographic database of research articles, books and reports about aquatic plants.