Other varieties, such as duckweed, absorb nutrients by dangling roots in the water. Experts say aquatic weed control can be approached using three methods, singly or in combination. Most aquatic plants can reproduce by fragmentation, so cleanup will have to be repeated several times to eliminate new growth. Hartle explains that physical removal is effective only for small quantities of shoreline plants but reduces the rate of regrowth as well as the availability of nutrients. Mechanical plant harvesting is used only on large lakes.
Landowners also can alter a pond's environment to control vegetation.
Hartle says drawing down any pond larger than an acre requires a permit. In small ponds, aeration can partially control the growth of blue-green algae, but is ineffective on other plants. Biological Control Introducing vegetation-eating fish into a pond system can be very effective, particularly for submerged plants. Filamentous algae can be reduced somewhat as well. Hartle says the triploid grass carp, a fish genetically altered so it cannot reproduce, is the only effective biological vegetation control.