Aquatic herbicides vary in effectiveness (depending on the weed species), toxicity, and water-use restrictions. Selection of which herbicide to apply depends largely on the identification of the aquatic plant to be treated (Murphy and Shelton 1996). For example, algae (filamentous and single cell) problems are typically treated with herbicides containing copper. Submersed plants (coontail, elodea, and pondweed) are often treated with Fluridone and Diquat.
Aquatic plants growing in ponds and lakes are beneficial for fish and wildlife. They provide food, dissolved oxygen, and spawning and nesting habitat for fish and waterfowl. Aquatic plants can trap excessive nutrients and detoxify chemicals. Aquatic wildflowers such as the water lily are sold and planted to provide floral beauty to garden ponds. However, dense growths (over 25% of the surface area) of algae and other water plants can seriously interfere with pond recreation and threaten aquatic life.