The use of herbivorous fishes and other aquatic animals has been used for biological control of weeds. The biological control of aquatic weeds is easy and popular and is achieved by fishes those are phytophagus or herbivorous fishes. 4. A more detailed review of aquatic pesticide use can be found in Rutgers Cooperative Extension fact sheet FS386, ""Aquatic Weed Control" (Hart, 2001). This page is a general aquatic weed control guide. The concentration of chemical needed to control aquatic plants is often very small and is stated in parts per million (ppm). Biological Control of Aquatic Weed: There are large numbers of biological control methods. Chemical development and use was spurred by the realization that human- and machine-power were not able to keep up with the explosive growth of certain invasive plant species such as water hyacinth (Eichhornia crassipes) and hydrilla (Hydrilla verticillata). Since the late 1880s, various chemicals have been applied to our freshwater systems to control the growth of invasive aquatic plants. The aquatic weed category pages give additional information on the different species and specific treatment instructions and options. However, pond owners will be most suc-cessful in managing aquatic plants by using a variety of methods. Vegetation control may be accomplished with biological, mechanical, or chemi-cal methods. Using the aquatic herbicides suggested, you can get control of any aquatic weed species. The focus of this fact sheet is chemical control of aquatic plants with approved herbicides and algaecides. Aquatic Weed Control: How To Get Rid of Aquatic Weeds. A danger with any chemical treatment is the chance of oxygen depletion caused by the decomposition of dead plant material. For example, if the toxic concentration for a particular plant is 2 ppm, then the chemical should be applied at the ration of 2 parts of active ingredient to one million parts of water (2:1,000,000) in the area to be treated. measures or control measures.