Invasive non-indigenous weeds can be very harmful to the ecosystem of your lake or pond. Some invasive species of lake weeds are so aggressive that they will kill off all healthy lake plants and even harm lake animals.
The best way to control and remove aquatic weeds is to use are EPA certified herbicides. However if herbicides are administered incorrectly you can completely destroy all healthy lake plants and animals with the invasive weeds.
If you have a relatively complex lake or pond ecosystem it may be best to seek out the help of a professional to save time and money in the long run.