Why are the plants and algae important in an aquarium

Why is plants important the aquarium . Plants are important in a aquarium is because the Elodea helps the water stay clean so the fish don't die . The duckweed is important because if the fish did not duckweed they would of died so that is why duckweed is important to the fish. Then the Algae help filter the water . That why all of these things are important to the fish and the snails.